Synthesis and fungistatic activity of new groups of 2,4-dihydroxythiobenzoyl derivatives against phytopathogenic fungi

Twenty-six compounds, derivatives of amides, hydrazines, hydrazides, hydrazones, and semicarbazides, with a 2,4-dihydroxythiobenzoyl moiety, were synthesized from sulfinyl-bis(2,4-dihydroxythiobenzoyl). The compositions and chemical structures of these compounds were confirmed by IR, (1)H NMR, EI-MS, and elemental analysis. Antifungal properties of chemicals under in vitro conditions against five phytopathogenic fungi were estimated. In vivo studies against Erisiphe graminis were also carried out. The compounds N-substituted with an 2,4-dihydroxythiobenzamide group proved to be the most active. N-2-(1-Cinnamylbenzene ester)-2,4-dihydroxythiobenzamide, under in vitro conditions, showed activity at the level of 80-100% development of most pathogens at a concentration of 20 microg/mL and partially at a concentration of 200 microg/mL. For compounds with -HN-NH- or -NH-N= moiety, weak or no fungistatic properties were found at the concentrations studied.     

Chemistry and phytotoxicity of thaxtomin A alkyl ethers

The thaxtomin phytotoxins (1 and 2) from scab-producing Streptomyces pathogens of the potato are 2,5-dioxopiperazines consisting of modified l-tryptophanyl and l-phenylalanyl units. Thaxtomin A (1) is hydroxylated at C-14, the alpha carbon of the modified l-phenylalanyl moiety. Refluxing thaxtomin A in acidified MeOH, EtOH, and i-PrOH afforded C-14 thaxtomin A methyl- (3a and 3b), ethyl- (4a and 4b), and isopropyl- (5a and 5b) ethers, respectively, in both the 11S,14R (3a, 4a, and 5a) and 11S,14S (3b, 4b, and 5b) configurations. Crystal structures were determined for 3a and 4a. Extensive NMR as well as other spectroscopic data supported structural assignments for all of the derivatives. The 11S,14R-configured derivatives were slightly less potent than the natural products (1 and 2) as inhibitors of lettuce seedling root growth, whereas the activity of the 11S,14S epimers was much reduced, indicating that the configuration at C-14 found in the naturally occurring thaxtomins is essential for biological activity. Among the 11S,14R-configured compounds, potency decreased with an increasing size of the substituted alkoxy group.     

Synthesis and herbicidal evaluation of novel 3-[(alpha-hydroxy-substituted)benzylidene]pyrrolidine-2,4-diones

A series of 3-[(alpha-hydroxy-substituted) benzylidene]pyrrolidine-2,4-dione derivatives were synthesized as candidate herbicides by reacting different aroyl acetates with N-substituted glycine esters. The new compounds were identified by 1H NMR spectroscopy and elemental analyses. Their herbicidal activities were evaluated. Some compounds exhibited excellent herbicidal activities at a dose of 187.5 g/ha. A suitable electron-donating substituent at the 2- and/or 4-position of the phenyl ring was essential for high herbicidal activity, a result that has not been reported before. It was also found that the title compound's structure-activity relationships were different from those of other similar kinds of earlier compounds, a result that may depend on the enol structure difference.     

Synthesis of 3-(4-Bromobenzyl)-5-(aryl methylene)-5H-furan-2-ones and their activity as inhibitors of the photosynthetic electron transport chain

A series of 12 3-(4-bromobenzyl)-5-(arylmethylene)-5 H-furan-2-one lactones, designed using the naturally occurring toxin nostoclides as a lead structure, were synthesized and screened as potential inhibitors of photosynthetic electron transport. The structures were confirmed by (1)H and (13)C NMR, MS, and IR analyses. Their biological activity was evaluated both in vitro, as the ability to interfere with light-driven reduction of ferricyanide by isolated spinach chloroplasts, and in vivo, as the capability to inhibite the oxygen production by intact Chlorella cells. Some of the compounds exhibited inhibitory properties in the micromolar range against basal and phosphorylating electron flow from water to K 3[Fe(CN) 6], with no effect on uncoupled electron flow. Thus, they seem to behave as energy-transfer inhibitors. Although poor solubility in water may limit their effectiveness, the active derivatives could present structures to be exploited for the design of new substances endowed with herbicidal activity.     

Characterization of hemiacetal forms of anthocyanidin 3-O-beta-glycopyranosides

The 3-O-beta-glucopyranosides of delphinidin, petunidin, and malvidin (1-3) and cyanidin 3-O-beta-galactopyranoside (4) dissolved in deuterated methanolic solutions without and with acid (5%, CF3COOD) were identified by homo- and heteronuclear NMR techniques. The hemiacetal forms of all the four anthocyanins were characterized as two epimeric 2-hydroxy-hemiacetals on the basis of assignments of both proton and carbon NMR signals together with chemical shift considerations. This is the first report of 13C NMR assignments of two epimeric anthocyanin hemiacetal forms. No 4-hydroxy-hemiacetal form was detected for any of the pigments. For each anthocyanin dissolved in deuterated methanol, the equilibrium between each of the two epimeric hemiacetals and the corresponding flavylium cation was confirmed by the observed positive exchange cross-peaks in the 2D 1H NOESY spectra. The molar proportions of the flavylium cation and the two hemiacetals of 1-4 in deuterated methanol were very similar for all pigments, even during storage for weeks. The majority of the anthocyanins reported to occur in fruits have the same or similar structures as 1-4. These pigments have been proposed to exist predominantly as hemiacetals in slightly acidic to neutral solvents, which is a relevant pH range in plants and in the human gastrointestinal tract.     

Synthesis and antifungal activities of carabrol ester derivatives

Thirty-eight new ester derivatives of carabrol were designed, synthesized, and characterized by (1)H and (13)C NMR and HR-ESI-MS. Their antifungal activities against the fungal pathogen Colletotrichum lagenarium were evaluated using a spore germination assay. Of these 38 ester derivatives, 16 showed higher antifungal activity than that of carabrol and 7 showed higher antifungal activity than that of carabrone. It was found that the C-4 position of carabrol was a key position involving its antifungal activity, which showed the variation of 50% inhibition concentration (IC(50)) from 2.70 to 52.33 μg/mL. When substituted by the phenyl ring, the ester derivatives with electron-attracting groups showed higher activity than those with electron-donating ones. Two ester derivatives, carabryl 4-cynaobenzoate (II-17, IC(50) 2.70 μg/mL) and carabryl 4-isopropylbenzoate (II-27, IC(50) 2.82 μg/mL), showed only slightly lower antifungal activity than that of the positive control chlorothalonil (IC(50) 0.87 μg/mL) and have been identified as promising leads for development of new environmentally friendly fungicides.     

Isolation of novel glucosides related to gingerdiol from ginger and their antioxidative activities

Two novel glucosides of 6-gingerdiol were isolated from fresh ginger (Zingiber officinale Roscoe). Their structures were determined as 1-(4-O-beta-D-glucopyranosyl-3-methoxyphenyl)-3,5-dihydroxydecane (1) and 5-O-beta-D-glucopyranosyl-3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)deca ne (2) by HRFAB-MS and NMR analyses, and the absolute configurations of both aglycons were identified as (3S,5S) by a comparison with synthetic compounds. After incubating these glucosides with acetone powder prepared from fresh ginger, they were confirmed to have been hydrolyzed to 6-gingerdiol by HPLC. This result suggests that these glucosides are the precursors or intermediates of 6-gingerdiol. To recognize their function, their antioxidative activities were investigated and compared to that of their aglycon, 6-gingerdiol, by a linoleic acid model system and by their DPPH radical-scavenging ability. Although 1 did not indicate any activity, 2 had as strong activity as the aglycon in both measurements.     

Chemistry and bioactivity of royal jelly from Greece

Twenty-five compounds were identified from the dichloromethane and methanol extracts of royal jelly from Greece. Among them, 16 compounds are reported for the first time as royal jelly constituents, whereas 7 of them are isolated for the first time as natural products. The 7 new compounds were fatty acid derivatives: 10-acetoxydecanoic acid (1), trans-10-acetoxydec-2-enoic acid (2), 11-oxododecanoic acid (3), (11S)-hydroxydodecanoic acid (4), (10R,11R)-dihydroxydodecanoic acid (5), 3,11-dihydroxydodecanoic acid (6), and (11S),12-dihydroxydodecanoic acid (7). The structures of the isolated compounds were determined by spectroscopic methods, mainly by the concerted application of 1D and 2D NMR techniques (HMQC, HMBC) and mass spectrometry. The studied sample and the isolated compounds were tested for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungi and exhibited interesting activities.     

Synthesis and herbicidal activity of diphenyl ether derivatives containing unsaturated carboxylates

A series of novel diphenyl ether derivatives containing unsaturated carboxylates were designed and synthesized. Their structures were identified by (1)H nuclear magnetic resonance and elemental analyses. The bioassays indicated that the compounds 5b and 5c exhibited good herbicidal activities against velvetleaf at a concentration of 30-40 g/hm(2). The relationship between structure and herbicidal activity was also discussed. Among unsaturated carboxylates group, butenoate is the most promising one. Amonst them, 4-ethoxy-4-oxobutenyl 5-(2-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenzoate 5b was identified as the most promising candidate due to its high protoporphyrinogen IX oxidase inhibition effect (pI(50) = 6.64) and good herbicidal activity against broadleaf weeds with selectivity to soybean and low toxicity to mammals.     

Pyrazole derivatives as photosynthetic electron transport inhibitors: new leads and structure-activity relationship

Four series of new pyrazoles, namely, 5 4-carboxypyrazolo-3-tert-butylcarboxamide and 6 4-carboxypyrazolo-3-cyclopropylcarboxamide derivatives and 10 pyrazolo[3,4-d][1,3]thiazine-4-one and 9 pyrazolo[3,4-d][1,3]thiazine-4-thione derivatives, were synthesized and screened as potential inhibitors of photosynthetic electron transport. The structures were confirmed by 1H NMR, elemental, and IR analyses. Their biological activity was evaluated in vitro as the ability to interfere with the light-driven reduction of ferricyanide by isolated spinach chloroplasts. Only a few compounds exhibited excellent inhibitory properties in the micromolar range, comparable to those of commercial herbicides sharing the same target, such as diuron, lenacil, and hexazinone. Nevertheless, most of the remaining molecules exerted a remarkable inhibition in the millimolar range. Combined with previous results on 6 pyrazolo[1,5-a][1,3,5]triazine-2,4-dione and 4 pyrazolo[1,5-c][1,3,5]thiadiazine-2-one derivatives, these data allowed a comprehensive analysis of structure-activity relationship. Molecular modeling studies were undertaken to rationalize the structural determinants of activity in terms of shape, size, and molecular fields. Results suggested that the inhibitory potential of these compounds is associated mainly with their electrostatic properties.     

Antimicrobial properties of Quercus ilex L. proanthocyanidin dimers and simple phenolics: evaluation of their synergistic activity with conventional antimicrobials and prediction of their pharmacokinetic profile

The antibacterial and antifungal activities of an ample number of phenolic compounds isolated from Quercus ilex leaves, belonging to the classes of flavonoids, proanthocyanidins, and phenolic acids, are discussed. The isolation of A type proanthocyanidin, (+)-epigallocatechin-(2β→O→7, 4β→8)-(+)-catechin is reported for the first time. Its structure was established by means of highfield NMR (correlation spectroscopy, heteronuclear single quantum correlation, heteronuclear multiple bond correlation, and rotating frame Overhauser effect spectroscopy) and MS spectral analyses, while its absolute configuration was determined by circular dichroism measurements. The isolated compounds were tested for their antimicrobial effects against eight human bacterial species and 14 fungal species. In a second step, the most potent compounds were tested in combination with the conventional fungicides, bifonazole and ketoconazole, to evaluate possible synergistic effects. Results showed that proanthocyanidins 3 and 4 when combined with bifonazole and ketoconazole increase the activity of both of these conventional fungicides. Moreover, the pharmacokinetic profile of the isolated compounds was investigated using computational methods.     

Sesamolinol glucoside, disaminyl ether, and other lignans from sesame seeds

The application of a procedure based on XAD-4 adsorption resin permitted the obtainment of an enriched polyphenolic extract from Sesamum indicum seeds. Chemical analysis of the obtained extract led to the identification of 12 lignans. Among them, 2 lignans, (+)-sesamolinol-4'-O-β-D-glucoside and disaminyl ether, are reported for the first time as natural compounds. Their structure has been determined by spectroscopic methods, mainly by the application of one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) techniques [heteronuclear multiple-quantum coherence (HMQC), heteronuclear multiple-bond correlation (HMBC), and nuclear Overhauser effect spectrometry (NOESY)] and mass spectroscopy. The isolated compounds were evaluated for their antimutagenic activity. Among the tested lignans, the most active lignan was found to be sesamolin, followed by sesamolinol and samin, against H(2)O(2). Additionally, some of the tested lignans showed desmutagenic activity against benzo[a]pyrene (BaP).     

Structural characterization of lignin from triploid of Populus tomentosa Carr

To improve yields while minimizing the extent of mechanical action (just 2 h of planetary ball-milling), the residual wood meal obtained from extraction of milled wood lignin (MWL) was sequentially treated with cellulolytic enzyme and alkali, and the yields of MWL, cellulolytic enzyme lignin (CEL), and alkaline lignin (AL) were 5.4, 23.2, and 16.3%, respectively. The chemical structures of the lignin fractions obtained were characterized by carbohydrate analysis, gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) spectroscopy, and various advanced NMR spectroscopic techniques. The results showed that the lignin isolated as MWL during the early part of ball milling may originate mainly from the middle lamella. This lignin fraction was less degradable and contained more linear hemicelluloses and more C═O in unconjugated groups as well as more phenolic OH groups. Both 1D and 2D NMR spectra analyses confirmed that the lignin in triploid of Populus tomentosa Carr. is GSH-type and partially acylated at the γ-carbon of the side chain. Two-dimensional heteronuclear single-quantum coherence (13C-1H) NMR of MWL, CEL, and AL showed a predominance of β-O-4' aryl ether linkages (81.1-84.5% of total side chains), followed by β-β' resinol-type linkages (12.2-16.4%), and lower amounts of β-5' phenylcoumaran (2.1-2.6%) and β-1' spirodienone-type (0.4-1.4%) linkages. The syringyl (S)/guaiacyl (G) ratios were estimated to be 1.43, 2.29, and 2.83 for MWL, CEL, and AL, respectively.     

Enzymatic dehydrogenative polymerization of urushiols in fresh exudates from the lacquer tree, Rhus vernicifera DC

Fresh exudates from the lacquer tree, Rhus vernicifera DC, were extracted with acetone and the solution was chromatographed to isolate monomer, dimer, trimer, and oligomer fractions of urushiols. Constituents of the monomeric and dimeric fractions were then identified by two-dimensional (2D) 1H-13C heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond coherence (HMBC) NMR spectroscopic techniques. The results showed that the monomeric fraction contained 3-[8'Z,11'E,13'Z-pentadecatrienyl]catechol (1), 3-[8'Z,11'Z,14'-pentadecatrienyl]catechol (2), and 3-pentadecanyl]catechol (3), which was verified by HPLC analysis. The dimeric fraction contained 8'-(3' ',4' '-dihydroxy-5' '-alkenyl)phenyl-3-[9'E,11'E,13'Z-pentadecatrienyl]catechol (4), 14'-(3' ',4' '-dihydroxy-5' '-alkenyl)phenyl-3-[8'Z,10'E,12'E-pentadecatrienyl]catechol (5), 2-hydroxyl-3- or -6-alkenylphenyl ethyl ether (6), 14'-(3' ',4' '-dihydroxy-2' '-alkenyl)phenyl-3-[8'Z,10'E,12'E-pentadeca-trienyl]catechol (7), 15'-(2' '-hydroxy-3' '- or -6' '-alkenyl)phenyloxy-3-[8'Z,11'Z,13'E)-pentadecatrienyl]catechol (8), 14'-(2' ',3' '-dihydroxy-4' '-alkenyl)phenyl-3-[8'Z,10'E,12'E-pentadecantrienyl]catechol (9), 1,1',2,2'-tetrahydroxy-6,6'-dialkenyl-4,3'-biphenyl (10), 1,1',2,2'-tetrahydroxy-6,6'-dialkenyl-4,4'-biphenyl (11), 1,1',2,2'-tetrahydroxy-6,6'-dialkenyl-5,4'-biphenyl (12), and 1,2,1'-trihydroxy-6,6'-dialkenyldibenzofuran (13) as constituents. In addition, dimeric ethers and peroxides, such as compounds 14 and 15, were produced by autoxidation of monomeric urushiols in atmospheric air. The possible reaction mechanisms for the dehydrogenative polymerization of urushiols by Rhus laccase present in the fresh raw exudates under the atmospheric oxygen are discussed on the basis of structures identified. This is of primary importance because the use of the urushi exudates as coating materials does not involve organic solvents and is an environmentally friendly process.     

Insect pest management agents: hormonogen esters (juvenogens)

The chemical part of this investigation focused on designing structures and synthesizing a series of six new esters (juvenogens), derived from biologically active insect juvenile hormone bioanalogues (juvenoids, JHAs) and unsaturated short-chain linear and branched fatty acids for possible application as biochemically targeted insect hormonogen agents. The structures of the new compounds were assigned on the basis of a detailed NMR analysis of their (1)H and (13)C NMR spectra. The biological part of this investigation focused on introductory biological screening tests with these compounds against the red firebug (Pyrrhocoris apterus), termites (Reticulitermes santonensis and Prorhinotermes simplex), and the blowfly (Neobellieria bullata). The biological activity of the juvenogens was studied in relation to the fatty acid functionality in the structures. Notable biological activity in topical tests and medium activity in peroral tests was found for the juvenogens 3 and 7 with P. apterus. The compounds 6 and 8 showed the lowest activity in both topical and oral assays with P. apterus. Considerable effect of all tested juvenogens was observed in P. simplex; however, the juvenogens 5 and 6 (derivatives of the only branched short-chain fatty acid) showed no activity against R. santonensis. The effect of the compounds 3-8 on larval hatching of N. bullata was only moderate (larval hatching 80-90%); however, the proliferation effect caused by 5, 6, and 8 is more pronounced than the effect caused by 3, 4, and 7.     

Epicatechin carbonyl-trapping reactions in aqueous maillard systems: Identification and structural elucidation

Recently, our group reported via labeling experiments that epicatechin in Maillard reaction aqueous glucose-glycine model systems formed adduct reaction products with C2, C3, and C4 sugar fragments. In the current study, we investigated the identity of the sugar fragment precursors responsible for adduct generation by directly comparing the liquid chromatography-mass spectrometry properties of these reported epicatechin (EC)-sugar fragments adducts with those generated from reactions consisting of only EC and well-known Maillard-generated glucose fragments (i.e., glyoxal, glycolaldehyde, methylglyoxal, glyceraldehyde, etc.). The structural properties of an EC-methylglyoxal adduct reaction product were also analyzed by NMR. The most likely precursors for the C2, C3, and C4 sugar moiety of the EC-sugar fragment adducts were identified as glyoxal, hydroxyacetone, and erythrose, respectively. 1H NMR analysis of the EC-methylglyoxal indicated that the analyte underwent rapid conformational/constitutional exchange. Using cold temperature (-25 degrees C) two-dimensional NMR analyses (heteronuclear multiple bond coherence, heteronuclear multiple quantum coherence, and 1H-(1)H correlation spectroscopy), the structure of one of the isomers was reported to consist of a covalent linkage between the C1 position of the methylglyoxal and either the C6 or the C8 position of the EC A ring, presumably generated by hydroxyalkylation and aromatic substitution reactions.     

Flavonoid oxidation by the radical generator AIBN: a unified mechanism for quercetin radical scavenging

Four oxidized flavonoid derivatives generated from reacting quercetin (a pentahydroxylated flavone) with the peroxyl radical generator 2,2'-azobis-isobutyronitrile (AIBN) were isolated by chromatographic methods and identified by NMR and MS analyses. Compounds included 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (2); 1,3,11a-trihydroxy-9-(3,5,7-trihydroxy-4H-1-benzopyran-4-on-2-yl)-5a-(3,4-dihydroxyphenyl)-5,6,11-hexahydro-5,6,11-trioxanaphthacene-12-one (3); 2-(3,4-dihydroxybenzoyloxy)-4,6-dihydroxybenzoic acid (4); and methyl 3,4-dihydroxyphenylglyoxylate (5). Product ratios under different hydrogen ion concentrations and external nucleophiles revealed that two of the products, namely the substituted benzofuranone (2) and the depside (4), are generated from a common carbocation intermediate. Indirect evidence for the operation of a cyclic concerted mechanism in the formation of the dimeric product (3) is provided. The identification of these products supports the model that the principal site of scavenging reactive oxygen species (ROS) in quercetin is the o-dihydroxyl substituent in the B-ring, as well as the C-ring olefinic linkage.     

Interpretation of heteronuclear and multidimensional NMR spectroscopy of humic substances

Mapping the chemical structures and organization of humic substances is vital for a fundamental understanding of their roles and interactions in the soil. One‐dimensional nuclear magnetic resonance (NMR) techniques have advanced our awareness of the composition of humic materials, but modern developments in two‐dimensional NMR are soon likely to make obsolete reliance on one‐dimensional spectra alone. The advantages of using heteronuclear two‐dimensional NMR spectroscopy are illustrated in this paper in studies of the structural units in a fulvic acid fraction isolated from the Bh horizon of a Podzol. The structures identified from the NMR (at 500 MHz) experiments can be summarized as: mono‐ and dicarboxylic acids (in about equal amounts), with an average chain length of about 10 carbon atoms (these are easily the major components); smaller amounts (about 10–20% of the acids) of esters and alcohols or ethers; some carbohydrate and amino acid residues (evidence from chemical shift data would suggest that these were likely to be in the form of chains); and very small amounts of 1,2‐, 1,4‐, and 1,3,4‐substituted benzenes and of cinnamic acids. The results suggest that applications of heteronuclear and multidimensional NMR spectroscopy will allow considerable progress to be made in understanding the nature of the structural units and their connectivities in humic molecules provided that the heterogeneity of the humic mixtures can first be decreased significantly.     

Antifungal activity and biotransformation of diisophorone by Botrytis cinerea

Diisophorone (1) was tested against two strains of the necrotrophic plant pathogen Botrytis cinerea.Fungal sensitivity varied according to the strain. B. cinera 2100 was more sensitive than B. cinereaUCA992: its mycelial growth was significantly inhibited at concentrations of 50 ppm and above. Although diisophorone (1) showed an effective control of B. cinerea, a detoxification mechanism was present. The detoxification of racemic diisophorone (1) by B. cinerea was investigated. Incubation with two strains of B. cinerea gave one and four biotransformation products (2-5), respectively. Their structures were established as the known 8beta-hydroxydiisophorone (2), 6alpha-hydroxydiisophorone (3), 6beta-hydroxydiisophorone (4) and 8beta,14beta-dihydroxydiisophorone (5) on the basis of their spectroscopic data, including two-dimensional NMR analysis [heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple bond correlation (HMBC), and nuclear Overhauser enhancement spectroscopy (NOESY)] and an X-ray crystallographic study.     

Identification of antioxidative flavonols and anthocyanins in Sicana odorifera fruit peel

Ten flavonols and three anthocyanins were identified in the fruit peel of melo?n de olor (Sicana odorifera), and their structures were established by spectrometric and spectroscopic (ESI-MS and NMR) techniques. One of the identified flavonols, quercetin 3-O-(6'-O-malonyl)-β-D-glucopyranoside 4'-O-β-D-glucopyranoside, has not been reported before in the plant kingdom. Although quercetin-3-O-α-L-rhamnopyranosyl-(1→6)-β-d-glucopyranoside-4'-O-β-D-glucopyranoside had been reported before in literature and structure elucidation was done by comparison of NMR data with published data, to the best of our knowledge complete 1D and 2D NMR data have not been not delineated so far. Moreover, the antioxidant activity of pure compounds was measured by ABTS assay. It was established that quercetin 3-O-α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside, quercetin-3-O-(6'-malonyl)-glucopyranoside, quercetin-3-O-β-D-glucopyranoside, and quercetin-3-O-α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside-4'-O-β-D-glucopyranoside contribute significantly to the antioxidant activity exhibited by the fruit peel methanolic extract.