1-s2.0-S1756464613000819-main

8/12/2019 1-s2.0-S1756464613000819-main

1/8

Important flavonoids and limonin in selected Thai

citrus residues

Vaniya Chinapongtitiwat, Saranya Jongaroontaprangsee, Naphaporn Chiewchan*,Sakamon Devahastin

Department of Food Engineering, Faculty of Engineering, King Mongkuts University of Technology Thonburi, 126 Pracha u-tid Road, Tungkru,

Bangkok 10140, Thailand

A R T I C L E I N F O

Article history:

Received 2 November 2012

Received in revised form

14 March 2013

Accepted 14 March 2013

Available online 6 April 2013

Keywords:

Citrus fruits

Dietary fibre

Flavanones

LimoninPolymethoxyflavones

A B S T R A C T

The distributions of important flavonoids and limonin in selected Thai citrus residues were

investigated in this study. The residues of interest were peels of pomelo (Citrus grandis(L.)

Osbeck cv. Kao Yai and cv. Kao Nampheung), residues after juice extraction of tangerine

(Citrus reticulataBlanco cv. Sainamphueng and cv. Bangmod) and peels and residues after

juice extraction of kaffi r lime (Citrus hystrixDC). Flavonoids were characterized and quan-

tified in terms of flavanones, i.e., naringin and hesperidin, and polymethoxyflavones

(PMFs), i.e., nobiletin, sinensetin and tangeretin. Naringin was a dominant flavanone in

polmelo peels. Three PMFs were found in all samples with varying contents. Comparing

the samples, residues from tangerine cv. Bangmod exhibited the highest value of each

PMFs. Limonin was present in small amounts in pomelo peels and residues after juice

extraction of tangerine and kaffir lime. All samples were good sources of dietary fibre, with

a total dietary fibre content of more than 60 g/100 g on a dry weight basis with high propor-

tion of soluble dietary fibre.

2013 Elsevier Ltd. All rights reserved.

1. Introduction

Citrus fruits are consumed either in their fresh or processed

form due to their pleasant flavour, refreshing juice and health

benefits. Many phytochemicals have been identified in citrus

fruits; these include vitamin C, carotenoids, flavonoids andlimonoids (Igual, Garca-Martnez, Camacho, & Martnez-

Navarrete, 2013). Citrus flavonoids have gained much interest

due to their chemoprotective effects. Citrus flavonoids exhibit

antioxidant, antimicrobial, anticarcinogenic, antiviral, anti-

allergic and anti-inflammatory activities (Benavente-Garca,

Castillo, Marn, Ortuno, & Del Ro, 1997; Ram & Singh, 2006).

They also inhibit human platelet aggregation (Benavente-

Garca et al., 1997; Kanadaswami et al. 2005). Moreover, citrus

fruits also contain high amounts of dietary fibre (DF) with well

balanced proportion of soluble dietary fibre (SDF) and insolu-

ble dietary fibre (IDF) (Baker, 1994).

There are many classes of flavonoids with flavanones

being the abundant group in citrus fruits (Peterson et al.,

2006; Ram & Singh, 2006). The most prevalent flavanones intissues and peels of citrus fruits are naringin and hesperidin

(Gattuso, Barreca, Gargiulli, Leuzzi, & Caristi, 2007; Stuetz,

Prapamontol, Hongsibsong, & Biesalski, 2010). Naringin

exhibits many health benefits, including an ability to prevent

cancer by suppression of carcinogenesis and inducing cell

apoptosis (Meiyanto, Hermawan, & Anindyajati, 2012).

Hesperidin has also been reported to reduce the proliferation

of many cancer cells (Nazari, Ghorbani, Hekmat-Doost,

1756-4646/$ - see front matter

2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.jff.2013.03.012

* Corresponding author. Tel.: +66 2 470 9243; fax: +66 2 470 9240.E-mail address:[email protected](N. Chiewchan).

J O U R N A L O F F U N C T I O N A L F O O D S 5 ( 2 0 1 3 ) 1 1 5 11 1 5 8

A v a i l a b l e a t w w w . s c i e n c e d ir e c t . c o m

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j f f
http://dx.doi.org/10.1016/j.jff.2013.03.012mailto:[email protected]://dx.doi.org/10.1016/j.jff.2013.03.012http://dx.doi.org/10.1016/j.jff.2013.03.012http://dx.doi.org/10.1016/j.jff.2013.03.012http://www.elsevier.com/locate/jffhttp://www.elsevier.com/locate/jffhttp://dx.doi.org/10.1016/j.jff.2013.03.012http://dx.doi.org/10.1016/j.jff.2013.03.012http://dx.doi.org/10.1016/j.jff.2013.03.012mailto:[email protected]://dx.doi.org/10.1016/j.jff.2013.03.012

8/12/2019 1-s2.0-S1756464613000819-main

2/8

Jeddi-Tehrani, & Zand, 2011; Park, Kim, Ha, & Chung, 2008)

and also possesses anti-inflamatory effect (Benavente-Garca

et al., 1997).

Flavones are also found in citrus fruits but at lower con-

centrations than flavanones. Flavones are generally found in

the oil glands of citus flavedo (Chen, Montanari, & Widmer,

1997). Polymethoxyflavones (PMFs), flavones bearing two or

more methoxy groups on their basic benzo-c-pyrone (15-car-

bon, C6C3C6) skeleton with a carbonyl group at the C4posi-

tion (Li et al., 2009), are of particular interest due to their

broad biological activities, including anticancer, anti-athero-

genic and anti-inflammatory activities (Du & Chen, 2010;

Lee et al., 2013; Li, Lo, & Yo, 2006; Ram & Singh, 2006). PMFs

that have typically been identified in citrus fruits include

nobiletin, sinensetin and tangeritin (Robards, Li, Antolovich,

& Boyd, 1997).

In addition to being a rich source of flavonoids, citrus fruits

also contain significant amounts of limonoids (Manners,

2007), which are a group of chemically related triterpene

derivatives found in citrus fruits and exist in many forms

(Hasegawa, 2000). Limonin is a major limonoid and is the pri-

mary cause of bitterness of citrus fruits (Hasegawa, Dillberger,

& Choi, 1984); the amount of limonin varies greatly depending

on the variety and part of the fruit (Ohta & Hasegawa, 1995).

Although limonoids are a major cause of bitterness in citrus

fruits, these compounds have been reported to possess

substantial anticancer and antiviral activities (Lam, Li, &

Hasegawa, 1989; Roy & Sara, 2006).

Many researchers have shown that citrus by-products are

a good source of DF (Jongaroontaprangsee et al., 2007;

Ubando-Rivera, Navarro-Ocana, & Valdivia-Lopez, 2005) as

well as phytochemicals (Pichaiyongvongdee & Haruenkit,

2009a, 2009b; Sun et al., 2010) and there is a potential to trans-

form citrus by-products into functional DF powder possessing

antioxidant and anticarcinogenic activities (Kuljarachanan,

Devahastin, & Chiewchan, 2009). Thailand has a wide variety

of citrus fruits that the bioactive compounds as well as DF

content in processing residues have never been fully charac-

terized. This work was therefore aimed at studying the

profiles of important flavonoids and limonin in selected Thai

citrus residues. The dietary fibre content in the residues was

also determined.

2. Materials and methods

2.1. Sample preparation

Fresh citrus fruits, i.e., pomeloes (Citrus grandis(L.) Osbeck cv.

Kao Nampheung and C. grandis (L.) Osbeck cv. Kao Yai), tan-

gerines (Citrus reticulataBlanco cv. Bangmod and C. reticulata

Blanco cv. Sainamphueng) and kaffir lime (Citrus hystrix DC)

with fresh appearance, free of rotting and bruising or any

other signs of deterioration were purchased from Pracha u-

tid 61 Market in Bangkok, Thailand. The sizes of pomeloes,

tangerines and kaffir limes used in the experiments were

170200, 3234 and 2530 mm, respectively. For pomeloes,

only their peels (albedo and flavedo) with an average thick-

ness of 2025 mm were used. After purchasing the samples

were kept at 4 C until the time of experiment, which was

on the same day of the purchase.

Prior to experiment, fruit samples were washed with tap

water and gently rubbed by a sponge. The washed fruits were

air dried at ambient temperature (28 C). Peels of pomeloes

and kaffir limes were taken off from the fruits. The peels were

cut into small pieces before being chopped by a chopper (War-

ing, Torrington, CT, USA). For the preparation of tangerine and

kaffir lime residues, fruits were cut into half and squeezed by

a hand-pressed juice extractor. The residues were cut into

small pieces and subsequently chopped by the chopper. The

particle size of the samples after chopping was approximately

13 mm. The prepared citrus residues were dried in a freeze

dryer until the moisture content was less than 10% on a dry

basis. The dried samples were vacuum-packed in aluminum

foil packets and kept at 18 C until further determination

of flavonoids, limonin and DF contents. All analyses were per-

formed within one week.

2.2. Determination of flavonoids contents

The flavonoids extraction method was as suggested bySene-

virathne, Joen, Ha and Kim (2009) with slight modifications.

One g of a sample was first mixed with 50 mL of methanol

and placed in an incubator shaker (New Brunswick Scien-

tific, Edison, NJ, USA) at 120 rpm at ambient temperature

(28 C) for one day; the content was then filtered through

Whatman No. 1 filter paper with the aid of a vacuum pump

(Gast, Benton Harbor, MI, USA). The extract solution was dis-

solved in 50 mL of methanol (AR grade) before further

analysis.

The flavonoid constituents were determined using high

performance liquid chromatography (HPLC) following the

method suggested byNogata et al. (2006)with some modifica-

tions. In brief, the sample extract was filtered through a 0.45-

lm nylon filter. Ten microlitres of the filtrate was injected into

a Symmetry C18 5lm (3.9 150 mm) HPLC column (Waters,

Milford, MA, USA). The HPLC system consisted of a pump

and controller (Waters, Milford, MA, USA) and photodiode ar-

ray detector (Waters, Milford, MA, USA). The mobile phase

was 0.01 M phosphoric acid (H3PO4) and methanol (MeOH,

HPLC grade). The gradient program was as follows:

(1) 055 min, 7055% (v/v) H3PO4 and 3045% (v/v) MeOH;

(2) 5595 min, 550% (v/v) H3PO4 and 45100% (v/v) MeOH;

(3) 95100 min, 100% (v/v) MeOH; the flow rate was set at

0.6 mL/min. A UV spectrophotometer detector at a wave-

length of 285 nm was used for detecting flavonoids. The

column temperature was maintained at 40 C.

The concentration of each flavonoid was calculated from

an integrated chromatographic peak area of the sample and

the corresponding standard; standard flavonoids consisted

of hesperidin, naringin, sinensetin, nobiletin and tangeretin.

2.3. Determination of limonin content

The limonin content was determined using HPLC following

the method ofSun, Chen, Chen, and Chen (2005) with slight

modifications as proposed by Kuljarachanan et al. (2009).

One gram of sample was mixed with 60 mL of dichlorometh-

ane and placed in the incubator shaker at 120 rpm at ambient

temperature (28 C) for 4 h; the content was then filtrered

through Whatman No. 1 filter paper with the aid of a vacuum

1152 J O U R N A L O F F U N C T I O N A L F O O D S 5 ( 2 0 1 3 ) 1 1 5 11 1 5 8

8/12/2019 1-s2.0-S1756464613000819-main

3/8

pump. The extract solution was evaporated to close to com-

plete dryness with a rotary evaporator (Resona Technics, Gos-

sau, Switzerland) at 30C for 20 min. The residues were

dissolved in 10 mL of acetonitrile (HPLC grade) and filtered

through a 0.45-lm syringe filter. Ten microlitres of the filtered

solution were then injected into a liquid chromatography

column.

Symmetry C18 5 lm (4.6 150 mm) HPLC column (Waters,

Milford, MA, USA) was used for limonin analysis. The HPLC

system consisted of a pump and controller (Waters, Milford,

MA, USA) and a tunable absorbance detector (Waters, Milford,

MA, USA). A mixture of methanol, acetonitrile and water

(1:37:62, v/v/v) was used as the mobile phase and its flow rate

was set at 1 mL/min. A UV spectrophotometer detector at a

wavelength of 210 nm was used for detecting limonin. The

mobile phase was degassed using an ultrasonic generator.

2.4. Determination of dietary fibre contents

Total dietary fibre (TDF), soluble dietary fibre (SDF) and insol-

uble dietary fibre (IDF) contents of a sample were determined

according toAOAC (2000)Method 991.43. In brief, a dried pow-

dery sample was first gelatinized with heat stable a-amylase

(SigmaAldrich, Steinheim, Germany). After gelatinization

the sample was digested with protease (SigmaAldrich,

Steinheim, Germany) and amyloglucosidase (SigmaAldrich,

Steinheim, Germany) to remove proteins and starch present

in the sample. Subsequently, IDF was filtered and the residue

was washed with warm distilled water. The filtrate and wash

water were combined and added with 4 volumes of 95% (v/v)

methanol at 60 C to precipitate SDF. The precipitate (residue)

was then filtered and weighed after drying at 105 C in a hot

air oven (Memmert, Schwabach, Germany). Both IDF and

SDF residues were corrected for proteins (Kjeldahl procedure),

ash (incinerating the sample at 525 C) and blank for the final

calculation of SDF and IDF contents. A blank sample was

evaluated along with the tested sample to measure any

contribution of the reagents on the residues.

2.5. Statistical analysis

All experiments were performed in duplicate and mean val-

ues (on dry basis) with standard deviations are reported.

The experimental data were analyzed using an analysis of

variance (ANOVA). Differences between mean values were

established using the Fishers test at 95% confidence. SPSS

software (version 17, SPSS Inc., Chicago, IL, USA) was used

to perform all the statistical calculations.

3. Results and discussion

3.1. Flavonoids contents in Thai citrus residues

Fig. 1shows a typical chromatogram of important flavonoids

in selected citrus residues. The quantitative determination of

the important flavonoids on a dry basis is given inTables 1

and 2. The results showed that the type and contents of flavo-

noids varied widely depending on the citrus species. It is

Sinensetin

Nobiletin

Tangeretin

Naringin

(a)

(b)Hesperidin

Fig. 1 Typical chromatograms of important flavonoids in (a) pomelo peels (Citrus grandis(L.) Osbeck cv. Kao Yai) and (b)

residues after juice extraction of tangerine (Citrus recticulataBlanco cv. Bangmod).

J O U R N A L O F F U N C T I O N A L F O O D S 5 ( 2 0 1 3 ) 1 1 5 11 1 5 8 1153

8/12/2019 1-s2.0-S1756464613000819-main

4/8

noted that naringin and hesperidin were the targeted flava-

nones while sinensetin, nobiletin and tangeretin were the tar-

geted polymethoxyflavones in this study.

Table 1lists the naringin and hesperidin contents of the

selected citrus residues. Naringin was noted to be a major fla-

vonoid in the peels of both varieties of pomeloes. Naringin

has also been reported to be a predominant flavanone in peels

and edible portions of many varieties ofC. grandis (Nogata

et al., 2006;Wang, Chuang, & Ku, 2007; Zhang, Duan, Zang,

Huang, & Liu, 2011). Although high concentrations of naringinwere noted in the peels of both varieties of pomeloes, the

amounts were still lower than those detected in grapefruit

(C. paradisi) peels (McIntosh & Mansell, 1997; Xu, Ye, Chen, &

Liu, 2007). Naringin contents reported here were also lower

than those reported previously for the same cultivars of

pomeloes. Pichaiyongvongdee and Haruenkit (2009a) deter-

mined the naringin contents in different parts of Thai pomelo

cultivars, including Kao Yai and Kao Nampheung. Naringin in

flavedo and albedo were separately determined; the sum of

the naringin contents in flavedo and albedo of pomeloes cv.

Kao Yai and Kao Nampheung were 16,929 and 25,071 ppm,

respectively. Cultural practice as well as cultivation area

might contribute to the variation of naringin in pomelo peelsof the same cultivar. Chaiwong and Theppakorn (2010) re-

ported that flesh ofC. grandiscv. Thong Dee grown in different

parts of Thailand possessed naringin content in the range of

254719 ppm.

On the other hand, only minute content of naringin was

observed in the residues after juice extraction of tangerine

cv. Sainamphueng, while no naringin was detected in the res-

idues after juice extraction of tangerine cv. Bangmod. The ab-

sence of naringin in many tangerine cultivars has also been

reported (Kawaii, Tomono, Katase, Ogawa, & Yano, 1999;

Nogata et al., 2006;Peterson et al., 2006).

In terms of hesperidin, this flavanone was not observed in

the selected pomelo peels. Previous works have indeed shown

that pomeloes contained small amounts of hesperidin

(Pichaiyongvongdee & Haruenkit, 2009b; Wang, Chuang, &

Ku, 2008; Wang et al., 2007), while some possessed no

hesperidin at all (Zhang et al., 2011).Pichaiyongvongdee and

Haruenkit (2009) also reported that many Thai cultivar of

pomeloes contained no hesperidin.

In contrast, hesperidin was note to be a major flavanone in

the residues after juice extraction of tangerine.Manthey and

Grohmann (1996)also reported that hesperidin is a main flav-

anoid in orange peels. The hesperidin contents in the resi-dues after juice extraction of tangerines reported here were

in similar order to those previously reported in orange peels

(19,17027,781 ppm) (Manthey & Grohmann, 1996) and much

higher than those reported in sour orange (C. Aurantium) peels

(Bocco, Cuvelier, Richard, & Berset, 1998) and Satsuma man-

darin (C. UnshiuMarc.) peels (Ma et al., 2008). Hesperidin con-

tent in the residues of tangerine cv. Bangmod was higher than

that of tangerine cv. Sainampheung. Tangerine cv. Sai-

nampheung nevertheless contained higher amount of hes-

peridin than hand-pressed juice and peeled fruit of the

same cultivar (Stuetz et al., 2010). Residues after juice extrac-

tion are indeed known to be a rich source of hesperidin than

the other fruit parts and its juice (Sun et al., 2010). Hesperidinwas also much more dominant than naringin in kaffir lime

residues.Berhow, Fong, and Hasegawa (1996)indeed reported

that hesperidin is abundant in the leaves ofC. Hystrix, while

naringin was not detected.

Since it has been reported that sinensetin, nobiletin and

tangeretin are PMFs commonly found in a wide variety of cit-

rus fruits (Manthey & Grohmann, 2001; Robards et al., 1997),

these PMFs were determined in this study. Table 2 lists the

amounts of PMFs found in various residues. All residues con-

tained three PMFs at different contents. The two tangerine

residues possessed more significant amounts of the three

PMFs comparing to the pomelo peels and kaffir lime residues.

The results were similar to those reported by Kawaii et al.

Table 1 Amount of flavanones (ppm) in Thai citrus residues.

Scientific name Cultivar Sample type Naringin content Hesperidin content

Citrus grandis(L.) Osbeck Kao Yai Peels 10.884 608a ND

Citrus grandis(L.) Osbeck Kao Namphueng Peels 11.875 955a ND

Citrus reticulataBlanco Sainamphueng Residues after juice extraction 176 1b 17.680 97a

Citrus reticulataBlanco Bangmod Residues after juice extraction ND 23.327 3856a

Citrus hystrixDC Kaffir lime Peels 149 43b 2.210 852b

Citrus hystrixDC Kaffir lime Residues after juice extraction 90 24b 5.326 152b

Same letters in the same column indicate that values are not significantly different (p> 0.05).

Table 2 Amount of polymethoxyflavones (ppm) in Thai citrus residues.

Scientific name Cultivar Sample type Sinensetin content Nobiletin content Tangeretincontent

Citrus grandis(L.) Osbeck Kao Yai Peels 29 19b 12 9c 14 2c

Citrus grandis(L.) Osbeck Kao Namphueng Peels 17 7b 11 3c 3 2

Citrus reticulataBlanco Sainamphueng Residues after juice extraction 201 40a 702 55b 498 20b

Citrus reticulataBlanco Bangmod Residues after juice extraction 208 5a 1.566 72a 1.361 276a

Citrus hystrixDC Kaffir lime Peels 28 17b

83 12c

7 3c

Citrus hystrixDC Kaffir lime Residues after juice extraction 46 32b 220 95bc 7 1c



8/12/2019 1-s2.0-S1756464613000819-main

5/8

(1999) who noted that Hirado Buntan (C. grandis) contained

only small amounts of nobiletin (1 ppm on a dry weight basis)

and tangeritin (7 ppm on a dry weight basis), while no sinese-

tin was detected in the edible parts (juice sac and segment

epidermis) of the fruit. Wang et al. (2007) also reported that

the edible portions of the two varieties ofC. grandis, i.e., Wen-

dun and Peiyou, contained sinensetin of only 2543 ppm on a

dry weight basis.

The above results illustrate that the residues obtained

from the two cultivars of Thai tangerine are good sources of

PMFs. Nobiletin and tangeretin contents noted in these two

samples were indeed much higher than those reported for

the edible parts (juice sac and segment epidermis) of Ponkan

(C. recticulata) and Ota Ponkan (C. recticulata) (Kawaii et al.,

1999). Sinensetin contents in the residues of both tangerine

cultivars were in the same order as those reported in the peels

of Ponkan (C. recticulata)(Wang et al., 2008).

Similar PMFs, i.e., sinensetin, nobiletin and tangeretin,

were observed previously in hand-pressed juice and peeled

fruits of tangerine cv. Sainampheung (Stuetz et al., 2010) but

the contents reported were much lower than those reported

here. The differences may arise from the different fruit parts

used in the experiments. Naturally, flavonoids distribute

throughout the fruit with varying amounts; peels, however,

accumulate the highest contents of flavonoids (Sun et al.,

2010). Residues after juice extraction of tangerine included

all parts of the fruit except juice and seeds. This made the res-

idues become the richer source of PMFs.

To the best of our knowledge, the profiles of PMFs in tan-

gerine cv. Bangmod have not previously been reported. It is

interesting that their PMFs contents were significantly higher,

especially nobiletin and tangeretin, than those of tangerine

cv. Sainampheung.

3.2. Limonin contents of Thai citrus residues

Fig. 2exemplifies a typical chromatogram of limonin in citrus

samples; the shown chromatogragphs belongs to the residues

after juice extraction of kaffir lime. Limonin contents in all

investigated citrus residues are given in Table 3. In general,

limonin is present in all citrus fruit tissues and the amount

varies widely depending on the variety, stage of fruit growth

and fruit part (McIntosh & Mansell, 1997;Sun et al., 2005).

Only small amounts of limonin were noted in peels of both

pomelo cultivars and the contents were similar to that found

in peels of grapefruit (C. Paradisi), which was in the range of

17.7107 ppm on a dry weight basis (McIntosh & Mansell,

1997). However, the limonin content noted in the present

work was much lower than that in Thai pomelo peels

(350535 ppm on a dry weight basis) as reported by

Pichaiyongvongdee and Haruenkit (2009). The limonin

contents in the residues after juice extraction of tangerine

Limonin

Fig. 2 Typical chromatogram of limonin in residues after

juice extraction of kaffir lime (Citrus hystrixDC).

Table 4 Amount of dietary fibre (g/100 g) in Thai citrus residues.

Scientific name Cultivar Sample type IDF content SDF content TDF content IDF:SDF (w/w)

Itrus grandis(L.) Osbeck Kao Yai Peels 52.13 4.95ab 30.55 0.76bc 82.69 2.83a 1.71:1

Citrus grandis(L.) Osbeck Kao Namphueng Peels 48.51 0.30bc 33.95 1.03a 82.46 0.73a 1.43:1

Citrus reticulataBlanco Sainamphueng Residues after juice extraction 36.38 0.09d 31.82 0.05ab 68.20 0.02c 1.14:1

Citrus reticulataBlanco Bangmod Residues after juice extraction 36.97 1.32d 27.76 1.86c 64.73 0.54c 1.33:1

Citrus hystrixDC Kaffir lime Peels 54.01 1.48a 28.13 0.52c 82.14 0.96a 1.92:1

Citrus hystrixDC Kaffir lime Residues after juice extraction 46.93 2.67c 28.10 1.63c 74.94 4.31bc 1.67:1


Table 3 Limonin content (ppm) of Thai citrus residues.

Scientific name Cultivar Sample type Limonin content

Citrus grandis(L.) Osbeck Kao Yai Peels 86 10b

Citrus grandis(L.) Osbeck Kao Namphueng Peels 41 5ab

Citrus reticulataBlanco Sainamphueng Residues after juice extraction 90 34b

Citrus reticulataBlanco Bangmod Residues after juice extraction 85 12b

Citrus hystrixDC Kaffir lime Peels 194 34c

Citrus hystrixDC Kaffir lime Residues after juice extraction 14 2a


J O U R N A L O F F U N C T I O N A L F O O D S 5 ( 2 0 1 3 ) 1 1 5 11 1 5 8 1155

8/12/2019 1-s2.0-S1756464613000819-main

6/8

cv. Sainamphueng and cv. Bangmod were not so high. The

limonin contents reported in this work were similar to those

reported byJungsakulrujirek and Noomhorm (1998)for peels

(albedo and flavedo) of Thai tangerine fruits (C. reticulataBlan-

co). Kaffir lime peels, on the other hand, possessed much

higher content of limonin.

3.3. Dietary fibre contents of Thai citrus residues

Dietary fibre (DF) contents and compositions of Thai citrus res-

idues are listed inTable 4. The results showed that all samples

were good sources of dietary fibre, containing total dietary fi-

bre of higher than 60 g/100 g on a dry weight basis with high

proportion of soluble dietary fibre which were even higher

than many other agricultural by-products such as residues

after juice extraction of peach (Grigelmo-Miguel & Martn-

Belloso, 1999), carrot pomace (Nawirska & Kwasniewska,

2005) and carrot peels (Chantaro, Devahastin, & Chiewchan,

2008). Pomelo peels of both cultivars and kaffir lime peels con-

tained similar DF contents of approximately 82 g/100 g on a

dry weight basis. The TDF content in peels of pomelo cv. Kao

Yai was similar to that in albedo of the same cultivar (78

80 g/100 g on a dry weight basis), while the SDF content was

lower than that reported by Naowakul, Wirjantoro, and

Phianmongkhol (2013). The TDF contents of the residues after

juice extraction of both varieties of tangerine were approxi-

mately 6568 g/100 g on a dry weight basis, which were higher

than the TDF content of peels of Thai Tangerine (C. reticulata

Blanco) (Attavanich & Anprung, 2003).

It is interesting to note that the SDF contents of all sam-

ples were in a similar order, while there was a wide variation

in the TDF contents. This was then resulted in the variation in

the IDF content and IDF:SDF ratio. Residues after juice extrac-

tion of tangerine possessed a better balance of IDF content

and SDF content than the other tested samples. Fibre source

suitable for use as a food ingredient should have an IDF:SDF

ratio close to 12.3 (Grigelmo-Miguel & Martn-Belloso, 1999).

Comparing between peels and residues after juice extrac-

tion of kaffir lime, it was observed that the peels contained

higher amount of IDF than the residues after juice extraction;

the SDF contents were nevertheless similar. In general, IDF is

a structure of natural cell walls, which are the main composi-

tion of fruit; IDF makes up about 2/3 of the fibre in most foods.

This is why the peels of citrus residues provided the higher

amount of IDF.

4. Conclusion

Important flavonoids and limonin in selected Thai citrus res-

idues were investigated. The results showed that types and

amounts of the phytochemicals of interest varied widely

depending on citrus variety as well as fruit part used for the

analysis. In terms of flavanones, pomelo peels was found to

be a rich source of naringin, while tangerine residues after

juice extraction were abundant in hesperidin. Three PMFs,

namely, sinensetin, nobiletin and tangeretin, were detected

in all samples with varying amounts; residues after juice

extraction of tangerine were again rich sources of PMFs. Only

small amount of limonin were detected in pomelo peels,

tangerine and kaffir lime residues. All samples also contained

well-balanced proportion of IDF and SDF in the range of 1.14

1.92.

Due to the high contents of beneficial phytochemicals and

DF, the investigated by-products may be used as raw materi-

als to produce DF associated with various bioactive com-

pounds. Study of the effects of pretreatment as well as

drying methods and conditions on the retention of the bioac-

tive compounds contained in the DF powder is suggested for

further study. The functional properties of the DF powder

should also be investigated.

Acknowledgements

The authors express their sincere appreciation to the Thai-

land Research Fund (TRF) and King Mongkuts University of

Technology Thonburi for supporting the study financially.

Author Jongaroontaprangsee thanks the TRF, through its Roy-

al Golden Jubilee (RGJ) Scholarship Program, and the Commis-

sion on Higher Education for supporting her doctoral study.

R E F E R E N C E S

AOAC. (2000). Official methods of analysis. Washington DC:Association of Official Analytical Chemists.

Attavanich, N., & Anprung, P. (2003). Dietary fibre powder fromCitrus reticulataBlanco peel and its application.Food, 33, 4555.

Baker, R. A. (1994). Potential dietary benefits of citrus pectin andfibre.Food Technology, 48, 133139.

Benavente-Garca, O., Castillo, J., Marn, F. R., Ortuno, A., & Del Ro,J. A. (1997). Uses and properties of citrus flavonoids.Journal of

Agricultural and Food Chemistry, 45, 45054515.Berhow, M. A., Fong, C. H., & Hasegawa, S. (1996). Limonoid andflavonoid composition in varieties of papeda andpapedocitrus.Biochemical Systematics and Ecology, 24, 237242.

Bocco, A., Cuvelier, M.-E., Richard, H., & Berset, C. (1998).Antioxidant activity and phenolic composition of citrus peeland seed extracts.Journal of Agricultural and Food Chemistry, 46,21232129.

Chaiwong, S., & Theppakorn, T. (2010). Bioactive compounds andantioxidant capacity of pink pomolo (Citrus grandis(L.) Osbeck)cv. Thong Dee) in Thailand. ISSAAS Journal, 16, 1016.

Chantaro, P., Devahastin, S., & Chiewchan, N. (2008). Production ofantioxidant high dietary fibre powder from carrot peels.LWT Food Science and Technology, 41(2008), 19871997.

Chen, J., Montanari, A. M., & Widmer, W. W. (1997). Two new

polymethoxylated flavones, a class of compounds withpotential anticancer activity, isolated from cold pressed Dancytangerine peel oil solids. Journal of Agricultural and FoodChemistry, 45, 364368.

Du, Q., & Chen, H. (2010). The methoxyflavones in Citrus reticulataBlanco cv. Ponkan and their antiproliferative activity againstcancer cells.Food Chemistry, 119, 567572.

Gattuso, G., Barreca, D., Gargiulli, C., Leuzzi, U., & Caristi, C. (2007).Flavonoid composition of citrus juices. Molecules, 12,16411673.

Grigelmo-Miguel, N., & Martn-Belloso, O. (1999). Comparison ofdietary fibre from by-products of processing fruits and greensand from cereals.LWT Food Science and Technology, 32,503508.

Hasegawa, S. (2000). Biochemistry of limonoids in citrus. In M. A.

Berhow, S. Hasegawa, & G. D. Manners (Eds.), Citrus limonoids:


8/12/2019 1-s2.0-S1756464613000819-main

7/8

8/12/2019 1-s2.0-S1756464613000819-main

8/8

Wang, Y.-C., Chuang, Y. C., & Ku, Y. H. (2007). Quantification ofbioactive compounds in citrus fruits cultivated in Taiwan.FoodChemistry, 102, 11631171.

Wang, Y.-C., Chuang, Y. C., & Ku, Y. H. (2008). The flavonoid,carotenoid and pectin content in peels of citrus cultivated inTaiwan. Food Chemistry, 106, 277284.

Xu, G., Ye, X., Chen, J., & Liu, D. (2007). Effect of heat treatment onthe phenolic compounds and antioxidant capacity of citrus

peel extract. Journal of Agricultural and Food Chemistry, 55,330335.

Zhang, M., Duan, C., Zang, Y., Huang, Z., & Liu, G. (2011). Theflavonoid composition of flavedo and juice from the pomelocultivar (Citrus grandis(L.) Osbeck) and the grapefruit cultivar(Citrus paradisi) from China. Food Chemistry, 129, 15301536.


Documents

1-s2.0-S1756464613000819-main