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Journal of Wood Chemistry and Technology

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Evaluation of the effect of inner and outer barkextracts of sugar maple (Acer saccharum var.saccharum) in combination with citric acid againstthe growth of three common molds

Mohamed Z. M. Salem, Maisa M. A. Mansour & Hosam O. Elansary

To cite this article: Mohamed Z. M. Salem, Maisa M. A. Mansour & Hosam O. Elansary (2019)Evaluation of the effect of inner and outer bark extracts of sugar maple (Acer�saccharum var.saccharum) in combination with citric acid against the growth of three common molds, Journal ofWood Chemistry and Technology, 39:2, 136-147, DOI: 10.1080/02773813.2018.1547763

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EVALUATION OF THE EFFECT OF INNER AND OUTER BARK EXTRACTS OFSUGAR MAPLE (ACER SACCHARUM VAR. SACCHARUM) IN COMBINATION WITHCITRIC ACID AGAINST THE GROWTH OF THREE COMMON MOLDS

Mohamed Z. M. Salem1, Maisa M. A. Mansour2, and Hosam O. Elansary3,4�1Faculty of Agriculture (EL-Shatby), Forestry and Wood Technology Department, AlexandriaUniversity, Alexandria, Egypt2Faculty of Archaeology, Conservation Department, Cairo University, Giza, Egypt3College of Food and Agriculture Sciences, Plant Production Department, King SaudUniversity, Riyadh, Saudi Arabia4Faculty of Agriculture (El-Shatby), Floriculture, Ornamental Horticulture, and Garden DesignDepartment, Alexandria University, Alexandria, Egypt

The bark of trees is an abundant material for chemical by-products. The combination effects ofdifferent concentrations of Acer saccharum var. saccharum inner (IB) and outer (OB) bark acet-one extracts with citric acid (CA) applied to Leucaena leucocephala wood were evaluated againstthe growth of three common molds (Trichoderma viride, Fusarium subglutinans, and Aspergillusniger). IB, OB, and CA solutions were prepared at 0.25% and 0.5% and their combinations wereformulated in equal amounts. Acetone extracts of IB and OB were analyzed for their chemicalscomposition and phenolic compounds using GC/MS and PHLC, respectively. The IB acetoneextract contained 4-hydroxy-4-methyl-2-pentanone (31.67%), palmitic acid (15.52%), and linoleicacid (11.14%), while the OB acetone extract contained 1,2-benzenedicarboxylic acid, bis(2-ethyl-hexyl) ester (9.34%), (Z,E)-9,12-tetradecadien-1-ol (8.86%), and cis-tetrahydro-6-methoxy-2H-pyran-3-ol (5.72%). The HPLC analysis indicated the presence of 14 phenolic compounds in IBextract with major constituents caffeine (362.88mg/g extract), and p-hydroxy benzoic acid(358.06mg/g extract), while OB contained 12 compounds with major constituents p-hydroxy ben-zoic acid (8950.5mg/g extract), gallic acid (5261mg/g extract) and salicylic acid (572.38mg/gextract). High total phenolic content in OB (292.67mg GAE/g) was associated with high antioxi-dant activity with an IC50 values of 1.77 and 4.14lg/mL, as measured by DPPH and b-Carotene-linoleic acid, respectively. The combination treatment of IB0.25%þ OB0.25%þCA0.25%produced the highest antifungal effects against growth of T. viride with an inhibition percentage(IP) of 10.37%, IB0.5%þCA0.5% (IP 16.66%) with F. subglutinans, while CA0.5% and OB0.25%,showed IP of 27.77% and 23.70% with A. niger, respectively. The combination effects of IB, OBand CA could be used as biocide agents for preventing mold growth on wood.

KEYWORDS. Sugar maple; antifungal activity; bark extracts; molds; combinations effects

INTRODUCTION

Molds cause discoloration on the surfacesof wood and wood-based products due to thepresence of spores and mycelial pigmentation,

but do not damage the structure of wood.[1–3]

Molds uses the carbohydrates, simple sugars,starch and organic materials as nutrient sourcesfor growth.[1–8]

Address correspondence to Mohemd Z. M. Salem, Faculty of Agriculture (EL-Shatby), Forestry and Wood TechnologyDepartment, Alexandria University, Alexandria, Egypt. E-mail: Mohamed-salem@alexu.edu.eg

�Present address: Department of Geography, Environmental Management and Energy Studies, University of Johannesburg,Auckland Park Kingsway Campus (APK) campus, 2006, South Africa.

Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lwct.

136

Journal of Wood Chemistry and Technology, 39:136–147, 2019# 2019 Taylor & Francis Group, LLCISSN: 0277-3813 print/1532-2319 onlineDOI: 10.1080/02773813.2018.1547763

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Cellulolytic enzymes such as tyrosinase andphenoloxidase are produced by Alternaria,Trichoderma, Aspergillus, Chaetomium andFusarium and can degrade wood.[9–12]

Pectinases, xylanases and arabinases areresponsible for the degradation action (cavityformation and erosion for Pinus halepensis andFicus sycomorus sapwoods) caused by A.niger.[13–16] b-glucosidase (degrades D-cellobiose to glucose) and amylase (degradesamylose in starch polymers) are produced asextracellular enzymes by Fusarium subglu-tinans.[17] Cellulases have been reported to beproduced by four Trichoderma sp.[18]

Botanical extracts exhibit promising anti-fungal activity against molds.[2,3,7,19–21] Citricacid is widely used to improve the woodproperties by modification of its chemicalstructure,[22,23] and as a natural wood adhe-sive.[24,25] Furthermore, a citric acid-glycerolmixture has been used as a resistant polymerfor Pine wood to improve the technical per-formance of products for outdoor uses.[26]

Leaves, bark, and sapwood extracts fromAcer saccharum have shown good anticanceractivity against colon tumor cells.[27] Leavescontain a high amounts of tannins,[28] and phe-nolics.[29] The polyphenolic compounds fromsap and sirup of A. saccharum have beenshown to be antioxidants, antiradicals and anti-mutagenics.[30] Scopoletin, a phenolic in thecoumarin family, has been isolated from sap,[31]

and is useful against hyperthyroıdy, lipid perox-ydation and hyperglycemia.[32] A. saccharumextracts from leaves,[33] and bark,[34] have alsoshown antibacterial properties.

Extracts from A. saccharum are reportedto contain four saccharumosides (A–D). Thesephenolic glycosides have been isolated frombark of sugar maple.[35] Acertannin isolatedfrom A. saccharum has shown antihyperglyce-mic effects on rats.[36] A mixture of phenolicextractives with antioxidant activities havebeen reported from sugar maple bark throughcatalytic organosolv pulping,[37] or optimizedhot water extraction.[38]

The aim of the present work was toevaluate the combination effects of extracts

from A. saccharum (inner and outer bark)with citric acid as antifungal agents againstthe growth of T. viride, A. niger, and F. sub-glutinans on Leucaena leucocephala wood.

MATERIALS AND METHODS

Preparation of Wood Blocks

Air-dried Leucaena leucocephala woodblocks with the dimensions of10� 10� 5mm were prepared at theDepartment of Forestry and WoodTechnology during January 2017. One hun-dred forty-four samples were prepared, auto-claved at 121 �C for 20min and cooled.

Preparation the concentrations of Acersaccharum var. Saccharum Bark Extractsand Citric Acid

Bark of Acer saccharum var. saccharum(Guelph, Ontario, Canada) was separatedinto inner (IB) and outer (OB) bark, air-driedunder laboratory conditions for two weeks,and then ground to powder (40–60 mesh)using a small laboratory mill. Fifty g fromeach of IB and OB ground samples weresoaked in 200ml of acetone solvent with stir-ring for 6 h at room temperature then thematerial was filtered using Watman No.1 fil-ter paper.[39] The solvent was evaporated at45 �C using a rotary evaporator. The crudeacetone extracts of IB and OB were stored insealed vials at 4 �C until further use. Theacetone extracts were prepared at the con-centrations of 0.25% and 0.5% by dissolvingin 10% dimethyl sulfoxide (DMSO, Sigma-Aldrich). Citric acid (CA) was prepared at0.25% and 0.5% (wt/wt).

Treatment of L. Leucocephala Wood bySoaking Method. Wood blocks weretreated with IB, OB, and CA all at concentra-tions of 0, 0.25 and 0.5% and their combina-tions with equal volume. Nine wood blocksof L. leucocephala were soaked in each treat-ment for 6 h for each fungus.[7]

EVALUATION OF THE EFFECT OF INNER AND OUTER BARK EXTRACTS OF SUGAR MAPLE 137

Antifungal Activity Test

Antifungal activity of the tested blocks wasassessed against the growth of Trichoderma vir-ide, Fusarium subglutinans, and Aspergillusniger (Microbiology Laboratory, ConservationDepartment, Faculty of Archaeology, CairoUniversity). The treated wood blocks wereplaced directly on potato dextrose agar (PDA)medium in petri dishes, then a 5mm diameterdisc cut from 15-day-old PDA culture of T. vir-ide, F. subglutinans, or A. niger was inoculatedon the treated wood. The petri dishes wereincubated for three days for T. viride and oneweek for F. subglutinans and A. nigerat 25±1 �C.

All the treatments were compared withwood treated with 70% ethanol. Linear fungalgrowth (mm) was assessed by measuring themarge of the clear inhibition zones (nogrowth of fungus) formed around the treatedwood once growth in the control treatment(wood without any treatments) reached 9 cm-diameter.[2,3,7,21] Inhibition percentage ofmycelia growth was calculated as follows:

Mycelial growth inhibition %ð Þ ¼ Ac�AtAc

� �� 100

where the AC and At are average diameters offungal colonies of control and treatment,respectively.

GC/MS Analysis of the Extracts

The chemical composition of acetoneextracts from IB and OB of A. saccharum var.saccharum was analyzed by GC/MS at theAtomic and Molecular Physics Unit,Experimental Nuclear Physics Department,Nuclear Research Centre, Egyptian AtomicEnergy Authority, Inshas, Cairo, Egypt, accord-ing previously published methods.[40–42] Theidentification of the chemical composition ofextracts was done on the basis of MS librarysearches (NIST and Wiley), and by comparingwith the MS literature data.[43,44] Xcalibur 3.0data system of GC/MS contained type thresholdvalues for match factors of Standard Index (SI)and Reverse Standard Index (RSI) to confirmthat all spectra are appended to the library. SI is

the match factor of getting mass spectrum andthe library spectrum. While RSI match factor ofgetting mass spectrum and the library spectrumignoring all peaks that are not in the libraryspectrum. The values of these two standardswere getting by mass spectrometer data base.

HPLC Condition forPhenolic Compounds

An Agilent 1260 Infinity HPLC Series(Agilent, USA), equipped with a Quaternarypump, a Zorbax Eclipse plus C18 column(100mm �4.6mm i.d.), (Agilent Technologies,USA), was operated at 30 �C. Separation wasachieved using a ternary linear elution gradientwith (A) HPLC grade water 0.2% H3PO4 (v/v),(B) methanol and (C) acetonitrile. The injectedvolume was 20lL. Detection: VWD detectorwas set at 284nm. The standard phenolic com-pounds used were gallic acid, catechol, p-hydroxy benzoic acid, caffeine, vanillic acid,caffeic acid, syringic acid, vanillin, p-coumaricacid, ferulic acid, ellagic acid, benzoic acid, o-coumaric acid, salicylic acid and cinnamic acid.

Determination of Total Phenolic andAntioxidant Activity

Total phenolic content was measuredspectrophotometrically by the Folin–Ciocalteumethod,[45] and antioxidant capacity wasassessed by the DPPH assay,[46] as well aswith the b-carotene-linoleic acid assay.[47]

Statistical Analysis

Results of the fungal growth inhibitionpercentage were analyzed in factorial designusing three factors (IB, OB, and CA) all at 3levels (0, 0.25 and 0.5%) with an ANOVAprocedure in SAS version 8.2.[48]

RESULTS AND DISCUSSION

Antifungal Activities of Extracts andTheir Combinations with Citric Acid

According to ANOVA tests (Tables 1–3),all the individual and the combination treat-ments were produced highly significanteffects on the growth of A. niger, F.

138 M. Z. M. SALEM ET AL.

subglutinans and T. viride, except the IB treat-ments on growth of A. niger (P¼ 0.0819).

The combination treatment ofIB0.25%þOB0.25%þCA0.25% was producedgreatest effect against growth of T. viride withan inhibition percentage (IP) of 10.37%, fol-lowed by OB0.5%þIB0.5% (8.14%) andCA0.25% (7.77%), which were higher thanthe PI value for 70% ethanol (1.85%).OB0.25%, OB0.5%, IB0.25%, IB0.5%, andtheir combinations of OB0.5%þCA0.5% andIB0.25%þOB0.25% showed no activityagainst the growth of T. viride. OB and IB at0.25% and 0.25% produced no activity buttheir combination (IB0.25%þOB0.25%þCA0.25%) had the highest activity (Table 4).

IB0.5%þCA0.5%,IB0.25%þOB0.25%þCA0.25%, andIB0.25%þCA0.25% produced IP values of16.66%, 13.70% and 13.33%, respectively,against F. subglutinans. These values werehigher than those for 70% ethanol (3.33%).The combination of OB0.25%þCA0.25% wasinactive against F. subglutinans, butOB0.25%, OB0.5%, IB0.5% and CA0.25%alone showed IP values of 8.88%, 10.00%,9.25% and 8.88%, respectively. On the otherhand, wood treated with CA0.5% producedan IP value of 0.74%, but the value wasenhanced to 16.66% when CA0.5% wascombined with IB0.5% (Table 4).

Wood treated with CA0.5%, OB0.25%,OB0.5%þIB0.5%, IB0.25%þOB0.25%þCA0.25%, or OB0.25þCA0.25%, showed IP val-ues for A. niger with 27.77%, 23.70%,17.77%, 16.29%, and 13.70%, respectively(Table 4).

Chemical Composition of Extracts, TotalPhenolic and Antioxidant Capacity

The main chemical components in the IBextract (Table 5) were 4-hydroxy-4-methyl-2-pentanone (31.67%), palmitic acid (15.52%),linoleic acid (11.14%), (1S,4S)-1-methyl-8-meth-ylenebicyclo[2.2.2]oct-5-en-2-one (10.99%), 9-octadecenoic acid (Z)-,2,3-dihydroxypropyl ester(10.53%) and stigmasterol (6.31%). Coniferyl

alcohol (4.12%) and syringic acid (5.43%) werealso reported (Table 5).

The main chemical compounds in theOB acetone extract of A. saccharum var. sac-charum were 1,2-benzenedicarboxylic acid,bis(2-ethylhexyl) ester (9.34%), (Z,E)-9,12-tet-radecadien-1-ol (8.86), cis-tetrahydro-6-

TABLE 1. ANOVA test for the effect of treatment combinationson the growth of A. niger.

Source ofvariance DF Type III SS

Meansquare F-value Pr> F

CA 2 778.27 389.14 42.09

methoxy-2H-pyran-3-ol (5.72%), phthalicacid, decylneopentyl ester (4.90%), 3-(1-ace-tyl-2,2-dimethyl-5-oxocyclopentyl)acrylic acid,methyl ester (4.01%), luteolin 6,8-di-C-gluco-side (3.5%), o-xylene (2.97%), and allyl cyclo-hexylcarbonate (2.67%) (Table 6).

Phytochemical screening of OB and IBextracts from A. saccharum (Table 7 andFigure 1) showed that 14 and 12 compounds

were in IB and OB acetone extracts, respect-ively. The major phenol compounds in IBacetone extract were caffeine (362.88 mg/gextract), p-hydroxy benzoic acid (358.06 mg/gextract), salicylic acid (123.24 mg/g extract),ellagic (108.74 mg/g extract) and gallic acid(60.52 mg/g extract), while vanillin was pre-sented at the lowest level (1.91 mg/g extract).The main phenolic compounds identified in

TABLE 4. Effects of different wood treatments on the growth inhibition (%) of A. niger, F. subglutinans, and T. viride.

Treatment concentration Growth inhibition (%)

OB IB CA A. niger F. subglutinans T. viride

0 0 0 0.00 0.00 0.000.25% 0 0 23.70±1.28 8.88±1.92 0.000.5% 0 0 10.37±1.69 10.00 ± 1.11 0.000 0.25% 0 6.29±3.57 5.92±2.31 0.000 0.5% 0 4.44±2.22 9.25±0.64 0.000 0 0.25% 1.48±1.69 8.88±2.93 7.77 ± 1.110 0 0.5% 27.77±2.22 0.74±1.28 2.96 ± 1.280.25% 0.25% 0 2.59±4.49 10.74±2.31 0.000.25% 0 0.25% 13.70±7.88 0.00 4.44±1.110 0.25% 0.25% 5.18±2.56 13.33±2.22 4.81 ± 1.280 0.5% 0.5% 18.14±2.31 16.66±3.33 0.000.5% 0 0.5% 12.22±2.22 2.22±1.11 0.000.5% 0.5% 0 17.77±1.11 0.74±1.28 8.14±2.790.25% 0.25% 0.25% 16.29±2.56 13.70±2.79 10.37±1.690.5% 0.5% 0.5% 8.14±1.28 4.44±1.11 3.70±1.28Ethanol 70% 22.59±5.01 3.33±1.92 1.85±1.69

IB: inner bark extract; OB: outer bark extract; CA: citric acid.Values are mean±SD.

TABLE 5. Chemical composition of the acetone inner bark extracts of A. saccharum.

RTa (min.) Compound name Compound percentage Molecular formula Molecular weight SIb RSIc

5.08 Coniferyl alcohol 4.12 C6H12O2 116 844 9005.38 Syringic acid 5.43 C16H12O4 268 915 9327.50 (1S,4S)-1-Methyl-8-

methylenebicy-clo[2.2.2]oct-5-en-2-one

10.99 C10H12O 148 924 996

7.674-Hydroxy-4-methyl-2-pentanone

31.67 C6H12O2 116 928 935

8.13 p-Xylene 4.29 C8H10 106 852 87922.94 Stigmasterol 6.31 C35H70 490 855 86323.07 Palmitic 15.52 C22H42O2 338 813 86223.32

9-Octadecenoic acid(Z)-, 2,3-dihydroxypropyl ester

10.53 C21H40O4 356 809 859

23.47 Linoleic 11.14 C26H50 362 605 620

aRT, Retention Time (min.).bSI, Standard Index.cRSI, Reverse Standard Index.

140 M. Z. M. SALEM ET AL.

TABLE 6. Chemical compositions of the acetone outer bark extracts of A. saccharum.

RTa (min.) Compound nameCompoundpercentage Molecular formula Molecular weight SIb RSIc

3.07 Tetrahydro-4-methyl-3-furanone 0.31 C5H8O2 100 695 8863.16 2,2-Dimethoxypropane 0.30 C5H12O2 104 582 8274.44 sec-Butyl acetate 1.12 C6H12O2 116 868 9204.67 2,2-dimethoxybutane 1.10 C6H14O2 118 814 8655.01 Phenyloxirane 1.45 C8H8O 120 739 7725.83 n-Butyl acetate 0.39 C6H12O2 116 656 7886.84 m-Xylene 0.83 C8H10 106 720 7816.99 o-Xylene 2.97 C8H10 106 819 8477.15 Cis-tetrahydro-6-methoxy-2H-

pyran-3-ol5.72 C6H12O3 132 687 827

7.63 p-Xylene 1.17 C8H10 106 829 8587.97 2-(2-Butoxyethoxy)ethanol 0.87 C8H18O3 162 602 7178.87 Propylbenzene 0.25 C9H12 120 632 8589.05 3-Ethyltoluene 0.95 C9H12 120 783 8679.20 4-Ethyltoluene 0.29 C9H12 120 695 8149.58 2,3-Dimethyl-4-pheny-l-3-oxa-

1-pentanol0.26 C12H18O2 194 481 712

9.86 1,2,3-Trimethylbenzene 0.99 C9H12 120 837 89423.53 1,1’-dodecylidenebis[4-methyl-

cyclohexane0.44 C26H50 362 440 448

23.65 1-Hexacosanol 1.31 C26H54O 382 427 44325.68 3,4,7-Trimethoxyquercetin 0.42 C18H16O7 344 418 43827.21 9-Hexylheptadecane 1.53 C23H48 324 430 45227.54 Methyl-13-oxooctadecanoate 1.07 C19H36O3 312 308 39828.24 2,2,4,10,12,12-Hexamethyl-7-

(3,5,5-trimethylhexyl)tridecane

1.29 C28H58 394 362 442

28.38 Luteolin 6,8-di-C-glucoside 3.5 C27H30O16 610 394 40128.58 17-Pentatriacontene 0.37 C35H70 490 512 52929.14 11-decyldocosane 1.29 C32H66 450 402 47329.99 1,4-dimethyl-2-octadecyl-

cyclohexane1.54 C26H52 364 506 521

30.41 Isohumulone 1.32 C21H30O5 362 342 39330.96 Octadecane, 3-ethyl-5-

(2-ethylbutyl)-1.48 C26H54 366 476 497

31.28 2-Hydroxy-5,6-epoxy-15-methyl- pregan-20-one

0.22 C22H34O3 346 391 452

31.45 Didodecyl phthalate 1.48 C32H54O4 502 448 70331.76 Dotriacontane 1.35 C32H66 450 379 44332.08 9-Dodecyltetradeca

hydro-anthracene1.21 C26H48 360 370 394

32.34 (Z,E)-9,12-Tetradecadien-1-ol 8.86 C14H26O 210 625 71732.69 Nonacosane 0.71 C29H60 408 497 52132.99 7-Methyl-Z,Z-8,10-

hexadecadien-1-ol acetate1.02 C19H34O2 294 381 453

33.32 Ethyl linoleate 1.41 C20H36O2 308 416 84733.63 9-Butyldocosane 0.86 C26H54 366 411 45334.09 (E)-Dodec-2-enylethyl carbonate 1.67 C15H28O3 256 327 47134.26 3-acetoxy-7,8-Epoxylanostan-

11-ol1.97 C32H54O4 502 423 428

34.59 Allyl cyclohexylcarbonate 2.67 C10H16O3 184 468 65834.82 5,14-Dibutyloctadecane 1.04 C26H54 366 396 42635.06 17-Pentatriacontene 1.91 C35H70 490 417 43235.25 Phthalic acid,

decylneopentyl ester4.90 C23H36O4 376 400 643

35.97 1,2-Benzenedicarboxylic acidbis(2-ethylhexyl) ester

9.34 C24H38O4 390 359 466

(Continued)

EVALUATION OF THE EFFECT OF INNER AND OUTER BARK EXTRACTS OF SUGAR MAPLE 141

OB acetone extract were p-hydroxy benzoicacid (8950.5mg/g extract), gallic acid (5261mg/g extract), salicylic acid (572.38mg/g extract),vanillin (435.49mg/g extract) and o-coumaricacid (163.09mg/g extract) and lowest com-pound was ferulic acid (41.93mg/g extract).

Stigmasterol, palmitic acid and linoleic acidhave been found in acetone–water extracts ofA. saccharum wood.[31] Compounds like pal-mitic acid, coniferyl alcohol, syringic acid, stig-masterol and stigmasta-3,5-dien-7-one werepreviously identified in ethanol bark extracts of

A. saccharum.[49] Palmitic acid has previouslybeen found in A. saccharinum extractives.[50]

Syringaldehyde, coniferyl alcohol, sinapalde-hyde, syringic acid, xanthene-9-carboxylic acid,stigmasterol, b-sitosterol, stigmastanol, and car-boxylic acid were also identified,[50,51] and theyall present interesting antioxidant properties.[52]

Homovanillic acid has been found in A. saccha-rinum sap.[53]

Extractive mixtures may produce someeffects against a particular species either byinhibiting cell wall synthesis or by causing celllyses or death.[54] For example, cinnamalde-hyde combined with catechin, quercetin oreugenol inhibits wood decay fungi due tointerference with fungal cell wall synthesisand a radical scavenging effects.[55]

Outer bark had the highest total phenoliccontent (292.67mg GAE/g), which resulted inhigh antioxidant activity with an IC50 value of1.77 and 4.14 lg/mL, as measured byDPPHand b-Carotene-linoleic acid, respect-ively. The OB extract had a high level ofextractives (7.82% w/w dry bark). Previouslyreports showed that bark had extraction yieldof 6.9–7.3% (w/w dry bark) with a TPC of298.6mg GAE/g.[38] Polyphenolic compoundsfrom A. saccharum have shown good antioxi-dant activity.[30] A recent study showed thatbark extract had a TPC of 19.04 g GAE/100 gDE,[56] with good antioxidant activity.[38,56]

High phenolic compounds resulted in highantioxidant activity of extracts.[57–59]

TABLE 6. (Continued).

RTa (min.) Compound nameCompoundpercentage Molecular formula Molecular weight SIb RSIc

36.29 3-(1-Acetyl-2,2-dimethyl-5-oxo-cyclopentyl)acrylic acid,methyl ester

4.01 C13H18O4 238 313 413

36.59 1,3,5-Trimethyl-2-octadecylcyclohexane

0.65 C27H54 378 444 457

37.24 5,6,7,3’,4’-Pentamethoxyflavone 0.65 C20H20O7 372 282 35037.45 9-Dodecyltetradeca

hydrophenanthrene1.18 C26H48 360 375 384

37.51 Methyl 5-allyloxytetronate 1.29 C8H10O4 170 269 48037.60 6-pentadecanyl-1-oxacyclo-

hexan-2-one0.98 C20H38O2 310 265 555

aRT, Retention Time (min.).bSI, Standard Index.cRSI, Reverse Standard index.

TABLE 7. Chemical composition analysis of phenoliccompounds of acetone extract from outer and inner bark of A.saccharum by HPLC.

Compound

mg/g extract

IB OB

Gallic acid 60.52 5261Catechol 38.84 –p-Hydroxy benzoic acid 358.06 8950.5Caffeine 362.88 531.86Vanillic acid 13.26 132.44Caffeic acid 4.84 46.42Syringic acid 3.67 60.24Vanillin 1.91 435.49p-Coumaric acid 44.13 42.71Ferulic acid 34.64 41.93Ellagic acid 108.74 –Benzoic acid – –o-Coumaric acid 45.17 163.09Salicylic acid 123.24 572.38Cinnamic acid 5.01 52.57

IB: inner bark extract; OB: outer bark extract.

142 M. Z. M. SALEM ET AL.

TABLE 8. Antioxidant activity and total phenolic content of inner and outer bark extracts of sugar maple.

Extract Extraction yield %a TPC (mg GAE/g)

IC50 (lg/mL)

DPPH b-Carotene-linoleic acid

Inner bark 6.06±0.89 190±10 3.40±0.64 6.57±0.32Outer bark 7.82±0.33 292.67±11.02 1.7 7±0.49 4.14±0.03BHT – – 2.9±0.2 2.6±0.1

All the values are mean±SD.IC50: concentration that caused a 50% inhibition of growth compared with control (The lowest values are the most active).TPC: Total phenolic compounds; TPC: Total phenolic content; .DPPH: 1,1-diphenyl-2-picrylhydrazyl; BHT: Butylated hydroxyl toluene.a% (w/w dry bark).

FIGURE 1. HPLC peaks of phenolic compounds identified in inner and outer bark acetone extracts of Sugar Maple.

EVALUATION OF THE EFFECT OF INNER AND OUTER BARK EXTRACTS OF SUGAR MAPLE 143

CONCLUSIONS

Application of bark extracts from Acersaccharum in combination with citric acid toL. leucocephala wood produced various activ-ities against three common molds (T. viride, F.subglutinans and A. niger). Synergistic effectswere noted for inner and outer bark extractsin combination with citric acid. The outerbark contained high total phenolic levels aswell as high levels of p-hydroxy benzoic acid,gallic acid and salicylic acid that was associ-ated with high antioxidant capacity. Thecombined effects of inner and outer barkwith citric acid could be useful tools for pro-tection wood against mold fungi.

DISCLOSURE STATEMENT

No potential conflict of interest wasreported by the authors.

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mkchap1547763_artidINTRODUCTIONMATERIALS AND METHODSPreparation of Wood BlocksPreparation the concentrations of Acer saccharum var. Saccharum Bark Extracts and Citric AcidTreatment of L. Leucocephala Wood by Soaking Method

Antifungal Activity TestGC/MS Analysis of the ExtractsHPLC Condition for Phenolic CompoundsDetermination of Total Phenolic and Antioxidant ActivityStatistical Analysis

RESULTS AND DISCUSSIONAntifungal Activities of Extracts and Their Combinations with Citric AcidChemical Composition of Extracts, Total Phenolic and Antioxidant Capacity

CONCLUSIONSDisclosure statementREFERENCES