Antitubercular activity of triterpenoids from Lippia turbinata

Assay-guided fractionation of the antitubercular MeOH-CH(2)Cl(2) extract obtained from Lippia turbinata led to the isolation of four novel triterpenoids-3beta,25-epoxy-3alpha,21alpha-dihydroxy-22beta-(3-methylbut-2-en-1-oyloxy)olean-12-ene-28-oic acid (1); 3beta,25-epoxy-3alpha,21alpha-dihydroxy-22beta-angeloyloxyolean-12-ene-28-oic acid (2); 3beta,25-epoxy-3alpha,21alpha-dihydroxy-22beta-tigloyloxyolean-12-ene-28-oic acid (3); and 3beta,25-epoxy-3alpha-hydroxy-22beta-(2-methylbutan-1-oyloxy)olean-12-ene-28-oic acid (4)-together with the known triterpenoids lantanilic acid (5), camaric acid (6), lantanolic acid (7), and rehmannic acid (8). The MIC values of 1-8 for growth inhibition of Mycobacterium tuberculosis were determined in the radiorespirometric BACTEC system.     

New lanostanoids, elfvingic acids A-H, from the fruit body of Elfvingia applanata

Eight new lanostanoids, 12alpha,15beta-dihydroxy-3,7,11,23-tetraoxolanost-8,(20Z)(22)-dien-26-oic acid (1), 7beta,8beta-epoxy-15beta,20S-dihydroxy-3,12,23-trioxolanost-9(11),16-dien-26-oic acid (2), 7beta,8beta-epoxy-3beta,15beta,20S-trihydroxy-12,23-dioxolanost-9(11),16-dien-26-oic acid (3), 7beta,8beta-epoxy-2alpha,3beta,15beta,20S-tetrahydroxy-12,23-dioxolanost-9(11),16-dien-26-oic acid (4), 7beta,8beta-epoxy-3beta,15beta,20S,28-tetrahydroxy-12,23-dioxolanost-9(11),16-dien-26-oic acid (5), 7beta,8beta-epoxy-3beta,15beta,19,20S-tetrahydroxy-12,23-dioxolanost-9(11),16-dien-26-oic acid (6), 8beta,15beta,20S-trihydroxy-3,7,12,23-tetraoxolanost-9(11),16-dien-26-oic acid (7), 7alpha,8alpha-epoxy-15beta,23xi-dihydroxy-12-oxo-3,4-secolanost-4(28),9(11),(20Z)(22)-trien-3,26-dioic acid (8), and the methyl ester of 8 (8a) were isolated from the fruit bodies of Elfvingia applanata. Their structures were established primarily by NMR experiments, and their biological activity against Kato III and Ehlrich cells was investigated.     

Chemical constituents of the aerial parts of Schnabelia tetradonta

A phytochemical study on the ethanol extract of the aerial parts of Schnabelia tetradonta led to the isolation of five new compounds, 1-5, together with seven known compounds. The structures of the new compounds were elucidated on the basis of spectral data interpretation as 2alpha,3alpha,23,29-tetrahydroxyolean-12-en-28-oic acid (1), 3-O-beta-d-glucuronopyranosyl-2beta,3beta,16beta-trihydroxy-28-norolean-12-en-15-on-23-oic acid (2), 21-O-beta-d-glucopyranosyl-3beta,21alpha,30-trihydroxyolean-13(18)-en-24-oic acid (3), 6-C-beta-l-arabinopyranosyl-8-C-alpha-l-arabinopyranosylapigenin (4), and 4-acetylaminoethylphenyl 1-O-[6-O-(Z)-p-methoxycinnamoyl-beta-d-glucopyranosyl(1-->2)]-[beta-d-glucopyranosyl(1-->3)]-alpha-l-rhamnopyranoside (5), respectively.     

猫耳刺中三萜类化合物的结构研究

目的：研究猫耳刺Ilex pernyi叶的化学成分。方法：应用硅胶及Sephadex LH-20凝胶柱色谱法对其化学成分进行分离,并利用NMR和MS等方法鉴定分离得到的化合物。结果：从猫耳刺的干燥叶中分离得到8个三萜化合物,分别鉴定为熊果酸(1),羽扇豆醇(2),α-香树脂醇(3),熊果醇(4),3β-羟基-乌索-11-烯-28,13β-内酯(5),坡模酸(6),羽扇-20(29)-烯-3β,24-二醇(7),3β,23-二羟基乌索-12-烯-28-酸(8),结论：该8个化合物均为首次从猫耳刺中分离得到。     

Triterpenoids from the resin of Styrax tonkinensis and their antiproliferative and differentiation effects in human leukemia HL-60 cells

Four new triterpenoids, 6beta-hydroxy-3-oxo-11alpha,12alpha-epoxyolean-28,13beta-olide (1), 3beta,6beta-dihydroxy-11alpha,12alpha-epoxyolean-28,13beta-olide (2), 3beta,6beta-dihydroxy-11-oxo-olean-12-en-28-oic acid (3), and 3beta-hydroxy-12-oxo-13Halpha-olean-28,19beta-olide (4), and five known triterpenes, 19alpha-hydroxy-3-oxo-olean-12-en-28-oic acid (5), 6beta-hydroxy-3-oxo-olean-12-en-28-oic acid (6), sumaresinolic acid (7), siaresinolic acid (8), and oleanolic acid (9), were isolated from the resin of Styrax tonkinensis. The structures of these triterpenoids were determined by physicochemical and spectroscopic methods. The configuration of compound 4 was confirmed by X-ray crystallographic analysis. All these triterpenoids inhibited HL-60 cell growth with IG(50) values ranging from 8.9 to 99.4 microM. Oleanolic acid (9) was the most effective antiproliferative agent, with an IG(50) value of 8.9 microM. While 3beta,6beta-dihydroxy-11-oxo-olean-12-en-28-oic acid (3) exhibited the least effective growth inhibition among these triterpenoids, it induced HL-60 cells to undergo differentiation as measured by an NBT reduction assay.     

Triterpenoid saponins of Acanthopanax nipponicus leaves

Five new triterpenoid saponins, nipponosides A-E (1, 3-6), were isolated from Acanthopanax nipponicus leaves, along with a known saponin, kalopanaxsaponin G (2). Nipponosides A-E were characterized as the 28-O-alpha-L-rhamnopyranosyl(1-->4)-beta-D-glucopyranosyl(1-->6)-beta -D-glucopyranosyl ester of 3-oxohederagenin, oleanolic acid 3-O-beta-D-glucopyranoside, gypsogenin 3-O-beta-D-glucopyranoside, 3beta,23,29-trihydroxyolean-12-en-28-oic acid, and 3beta,20alpha, 23-trihydroxy-30-nor-olean-12-en-28-oic acid, respectively. The structures of these new compounds were based on chemical and spectral methods.     

Monoterpene glycosides and triterpene acids from Eriobotrya deflexa

A phytochemical study on a methanolic extract of leaves of Eriobotrya deflexa led to the isolation and characterization of nine terpenoid compounds. Four of these are new chemical entities, including two monoterpene glycosides, (3S)-O-alpha-L-rhamnopyranosyl-(1-->3)-[4-O-(E)-coumaroyl]-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranosyl-linalool (1) and (3S)-O-alpha-L-rhamnopyranosyl-(1-->3)-[4-O-(Z)-coumaroyl]-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranosyl-linalool (2), and two triterpene acids, 1beta,2alpha,19alpha-trihydroxy-3-oxo-12-ursen-28-oic acid (3) and 2alpha,3alpha,19alpha-trihydroxy-12-oleanen-28-oic acid (4). Their structures were elucidated on the basis of spectroscopic analysis. The activities of these isolates in an in vitro antiproliferation test were also determined.     

委陵菜三萜成分研究

目的：研究委陵菜的化学成分及其抗癌活性。方法：用硅胶柱色谱、凝胶柱色谱等多种柱色谱分离,制备高效液相色谱纯化,得到单体化合物,用各种有机波谱鉴定化合物结构；并对化合物的抗癌活性进行研究。结果：分离得到15个三萜类化合物,鉴定为α-香树素(α-amyrin,1),β-香树素(β-amyrin,2),乌苏酸(ursolic acid,3),2α-羟基乌苏酸(corosolic acid,4),蔷薇酸(euscaphic acid,5),坡模酸(pomolic acid,6),委陵菜酸(tormentic acid,7),2α,3α-二羟基-12-烯-28-乌苏酸(2α,3α-dihydroxyurs-12-en-28-oic acid,8),2β,3β,19α-三羟基-12-烯-28-乌苏酸(2β,3β,19α-trihydroxyurs-12-en-28-oic acid,9),积雪草酸(asiatic acid,10),24-羟基委陵菜酸(24-hydroxy tormentic acid,11),2α,3α,19α,23-四羟基-12-烯-28-乌苏酸(myrianthic acid,12),齐墩果酸(oleanolic acid,13),2α-羟基齐墩果酸(maslinic acid,14),2α,3α-二羟基-12-烯-28-齐墩果酸(2α,3α-dihydroxyolean-12-en-28-oic acid,15)。结论：化合物1,2,4～15为首次从委陵菜中分离得到；化合物4,8～10,12,14和15对人宫颈癌细胞(Hela)和小鼠成纤维细胞(L929)具有一定的细胞毒作用,其中化合物4和9抗癌活性较强。     

Three new triterpenes from Nerium oleander and biological activity of the isolated compounds

New ursane-type triterpene 1, oleanane-type triterpene 2, and dammarane-type triterpene 15 were isolated from the leaves of Nerium oleander together with 12 known triterpenes, 3beta-hydroxy-12-ursen-28-oic acid (ursolic acid, 3), 3beta,27-dihydroxy-12-ursen-28-oic acid (4), 3beta,13beta-dihydroxyurs-11-en-28-oic acid (5), 3beta-hydroxyurs-12-en-28-aldehyde (6), 28-norurs-12-en-3beta-ol (7), urs-12-en-3beta-ol (8), urs-12-ene-3beta,28-diol (9), 3beta-hydroxy-12-oleanen-28-oic acid (oleanolic acid, 10), 3beta,27-dihydroxy-12-oleanen-28-oic acid (11), 3beta-hydroxy-20(29)-lupen-28-oic acid (betulinic acid, 12), 20(29)-lupene-3beta,28-diol (betulin, 13), and (20S,24R)-epoxydammarane-3beta,25-diol (14). On the basis of their spectroscopic data, the structures of the new compounds 1, 2, and 15 were established as 3beta,20alpha-dihydroxyurs-21-en-28-oic acid, 3beta,12alpha-dihydroxyoleanan-28,13beta-olide, and (20S,24S)-epoxydammarane-3beta,25-diol, respectively. The anti-inflammatory activity of the seven isolated compounds and methyl esters of ursolic acid and oleanoic acid in vitro was examined on the basis of inhibitory activity against the induction of the intercellular adhesion molecule-1 (ICAM-1). The anticancer activity of the 14 isolated compounds, including 1, 2, 15, and methyl esters of ursolic acid and oleanolic acid in vitro was examined on the basis of the cell growth inhibitory activities toward three kinds of human cell lines.     

New compounds from an extract of Vernonia colorata leaves with anti-inflammatory activity

Bioassay-directed fractionation of an anti-inflammatory CHCl(3)-MeOH (9:1) extract of leaves of Vernonia colorata, using a carrageenan-induced rat paw model, led to the isolation of six new compounds (1-6).These were assigned as two new androst-8-en glycosides, 3-O-[beta-d-galactopyranosyl-(1-2)-[beta-d-glucopyranosyl-(1-->6)]-beta-d-glucopyranoside]-5alpha,14alpha-androst-8-ene (1) and 3-O-[beta-d-glucopyranosyl-(1-->6)-beta-d-glucopyranoside]-5alpha,14alpha-androst-8-ene (2), two new stigmastane-type glycosides, 3beta,21,24-trihydroxy-21,23;22,28;26,28-triepoxy-5alpha-stigmasta-8(9),14(15)-dien-3-O-beta-d-galactopyranosyl-(1-->2)-beta-d-glucopyranoside (3) and 3beta,21,24-trihydroxy-21,23;22,28;26,28-triepoxy-5alpha-stigmasta-8(9),14(15)-dien-3-O-beta-d-galactopyranosyl-(1-->2)-beta-d-(6-acetyl)glucopyranoside (4), and two new stigmastane-type steroids, 3beta,25,29-trihydroxy-5alpha-stigmasta-8(9),14(15),24Z(28)-triene (5) and 3beta,23,25-trihydroxy-24,28-epoxy-5alpha-stigmasta-8(9),14(15)-diene (6). The structures of 1-6 were elucidated by spectral and chemical studies. Compounds 1-6 were tested for the anti-inflammatory activity, but all were inactive or weakly inactive as anti-inflammatory agents.     

广西产美味猕猴桃根正丁醇部位化学成分研究

目的：研究广西产美味猕猴桃根正丁醇部位的化学成分。方法：应用色谱技术分离纯化，根据理化性质和波谱数据鉴定化合物结构。结果：从美味猕猴桃根正丁醇部位中分离并鉴定了6个化合物，分别为毛花猕猴桃酸B(1)，2α，3β，24 -三羟基-12-烯-28-乌苏酸(2)，2α，3α，24 -三羟基-12-烯-28-乌苏酸(3)，2α，3α，23-三羟基-12，20(30)-二烯-28-乌苏酸(4)，2α，3α，24-三羟基-12，20(30)-二烯-28-乌苏酸(5)，正丁基-O-β-D-吡喃果糖苷(6)。结论：化合物1～4，6均为首次从该植物中分离得到，其中化合物6为首次从猕猴桃属植物中分得。     

Silenosides A-C, triterpenoid saponins from Silene vulgaris.

Three new triterpenoid saponins named silenosides A-C (1-3) were obtained from the roots of Silene vulgaris. Their structures were elucidated by spectral and chemical methods as beta-D-galactopyranosyl(1-->2)-beta-D-glucuronopyranosyl-3beta- hydrox y-23-oxoolean-12-en-28-oic acid 28-O-beta-D-xylopyranosyl(1-->3)-beta-D-xylopyranosyl(1-->4)-alpha-L- rhamnopyranosyl(1-->2)-beta-D-fucopyranoside; 3-O-beta-D-galactopyranosyl(1-->2)-beta-D-glucuronopyranosyl-3beta , 16alpha-dihydroxy-23-oxoolean-12-en-28-oic acid 28-O-beta-D-xylopyranosyl(1-->4)-[beta-D-glucopyranosyl(1-->2)]-alpha -L-rhamnopyranosyl(1-->2)-beta-D-fucopyranoside; and 3-O-alpha-L-arabinopyranosyl(1-->3)-[beta-D-galactopyranosyl(1-->2 )]- beta-D-glucuronopyranosyl-3beta, 16alpha-dihydroxy-23-oxoolean-12-en-28-oic acid 28-O-beta-D-xylopyranosyl(1-->4)-[beta-D-glucopyranosyl(1-->2)]-alpha -L-rhamnopyranosyl(1-->2)-beta-D-fucopyranoside, respectively.     

Triterpenoids from Brazilian Ilex species and their in vitro antitrypanosomal activity

From the leaves of Ilex affinis and Ilex buxifolia, two adulterant species of "erva mate" (Ilex paraguariensis), three new triterpenoid glycosides were isolated. Affinoside 1 (3beta-O-[beta-D-glucopyranosyl-(1-->3)-[2-O-acetyl-(1-->2]]-alpha-L-arabinopyranosyl pomolic acid 28-O-beta-D-glucopyranosyl ester, 1) was isolated from I. affinis, while buxifolioside I (28-O-beta-D-glucopyranosyl ester of (20S)-3alpha,19alpha-dihydroxyurs-12-ene-23,28-dioic acid, 7) and buxifolioside II (28-O-beta-D-glucopyranosyl ester of (20S)-3beta,19alpha-dihydroxyurs-12-en-24,28-dioic acid, 8) were isolated from I. buxifolia. Along with these new compounds, ilexoside II (2), ursolic acid (3), 28-nor-ursolic acid (4), 3beta-O-acetylursolic acid (5), and uvaol (6) were also isolated. The observed results confirm the structural specificity of the I. paraguariensis triterpenoids and reinforce a previous proposal to detect mate adulteration by triterpenoid analysis. In addition, the in vitro antitrypanosomal activity of some Ilex triterpenoids is also reported.     

鹿蹄草化学成分研究

目的：研究鹿蹄草Pyrola calliatha全草的化学成分。方法：采用硅胶及Sephadex LH-20凝胶柱色谱法等分离化合物,运用波谱学方法确定结构；并对化合物1～4,6～9进行抗真菌活性测定。结果：从鹿蹄草全草中分离得到10个化合物,分别为梅笠草素(1),熊果醇(2),熊果酸(3),2β,3β,23-三羟基-12-烯-28-乌苏酸(4),胡萝卜苷(5),2α,3β,23,24-四羟基-12-烯-28-乌苏酸(6),大黄素(7),没食子酸(8),水晶兰苷(9),腺苷(10)。结论：化合物2,4,6,7,10为首次从该属植物中分离得到,化合物5,9为首次从该种植物中分离得到；化合物1,3,4,6,8对新生隐球菌、白色念珠菌、红色毛癣菌等真菌生长有不同的抑制作用,其中化合物1的抗真菌活性较强。     

Four cycloartane triterpenoids and six related saponins from Passiflora edulis

Four cycloartane triterpenes, cyclopassifloic acids A (1), B (2), C (3), and D (4), and six related saponins, cyclopassiflosides I (5), II (6), III (7), IV (8), V (9), and VI (10), were isolated from the leaves and stems of Passiflora edulis, and their structures were elucidated on the base of extensive NMR experiments and chemical methods. Cyclopassifloic acids A-D were assigned as 22(R), 24(S)-1alpha,3beta,22,24,31-pentahydroxy-24-methylcycloartan -28-oic acid; 24(S)-1alpha,3beta,24, 31-tetrahydroxy-24-methylcycloartan-28-oic acid; 20(S),24(S)-1alpha, 3beta,21,24,31-pentahydroxy-24-methylcycloartan-28-oic acid; and 22(R)-1alpha,3beta,22-trihydroxy-24-oxocycloartan-28-oic acid, respectively. Cyclopassiflosides I-VI, in turn, were established as the 28-O-beta-D-glucopyranosides of cyclopassifloic acids A-D. Finally, cyclopassiflosides III and V were demonstrated as the 28, 31-bis-O-beta-D-glucopyranosides of cyclopassifloic acids B and C, respectively. Also obtained in this investigation were the known compounds passiflorin (11) and passifloric acid (12).     

Biologically active triterpenoid saponins from Acanthopanax senticosus

Three new triterpenoid saponins, acanthopanaxosides A (1), B (7), and C (13), were isolated from the leaves of Acanthopanax senticosus, together with 12 known saponins. The structures of these new saponins were established as 3-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-30-nor-olean-12,20(29)-dien-28-oic acid 28-O-alpha-L-rhamnopyranosyl-(1-->4)-6-O-acetyl-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (1), 3-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl oleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1-->4)-6-O-acetyl-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (7), and 3-O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-3beta-hydroxyolean-12-ene-28,29-dioic acid (13), on the basis of spectroscopic analysis and chemical degradation. Among the known compounds, sessiloside and tauroside H1 are reported for the first time from A. senticosus. The biological activity of compounds 1-15 was examined against pancreatic lipase. Ciwujianoside C1 (6), tauroside H1 (11), 3-O-alpha-rhamnopyranosyl-(1-->2)-alpha-arabinopyranosyl mesembryanthemoidigenic acid (12), acanthopanaxoside C (13), sessiloside (14), and chiisanoside (15) inhibited pancreatic lipase activity in vitro. In turn, ciwujianosides C2 (3), D2 (5), C4 (8), and C3 (10) and hederasaponin B (9) enhanced this enzyme.     

南蛇藤茎的化学成分(英文)

目的:研究南蛇藤Celastrus orbiculatus Thunb.茎的化学成分。方法:采用硅胶、Sephadex LH-20和ODS柱色谱方法进行化合物的分离和纯化。根据理化性质和光谱数据鉴定化合物结构。结果:从南蛇藤茎的乙酸乙酯部位分离得到11个化合物,经鉴定分别为:3β-hydroxy-2-oxoolean-12-ene-22,29-lactone(1),2,6-二甲氧基苯醌(2),3-氧代齐墩果酸(3),24-去甲基齐墩果烷-12-烯-28-酸-3-酮(4),白头翁酸(5),香草酸(6),23-羟基齐墩果烷-12-烯-28-酸-3-酮(7),丁香酸(8),齐墩果酸(9),β-谷甾醇(10),β-胡萝卜苷(11)。结论:化合物1为新三萜化合物,化合物2-5和7为首次从该属植物中分离得到,化合物8和9为首次从该植物中分离得到。     

Bioactive 12-oleanene triterpene and secotriterpene acids from Maytenus undata

The aerial parts of Maytenus undata yielded four new 12-oleanene and 3,4-seco-12-oleanene triterpene acids, namely, 3-oxo-11alpha-methoxyolean-12-ene-30-oic acid (1), 3-oxo-11alpha-hydroxyolean-12-ene-30-oic acid (2), 3-oxo-olean-9(11), 12-diene-30-oic acid (3), and 3,4-seco-olean-4(23),12-diene-3, 29-dioic acid (20-epi-koetjapic acid) (5), together with the known 3, 11-dioxoolean-12-ene-30-oic acid (3-oxo-18beta-glycyrrhetinic acid) (4), koetjapic acid (6), and the 12-oleanene artifact 3-oxo-11alpha-ethoxyolean-12-ene-30-oic acid (7). Koetjapic acid (6) inhibited the growth of Staphylococcus aureus, methicillin-resistant S. aureus, and Pseudomonas aeruginosa, with an MIC range of 3.125-6.25 microg/mL. The new 3,4-secotriterpene acid 20-epi-koetjapic acid (5) potently inhibited rat neonatal brain microglia phorbol ester-stimulated thromboxane B(2) (IC(50) = 0.5 microM) and superoxide anion (IC(50) = 1.9 microM) generation.     

Potential antitumor-promoting diterpenoids from the stem bark of Picea glehni

A novel rearranged labdane-type diterpenoid, 19(4-->3)abeo-8alpha, 13(S)-epoxylabda-4(18),14-diene (1), and two new abietane-type diterpenoids, 19-nor-abieta-4(18),8,11,13-tetraen-7-one (2) and 12-hydroxydehydroabietic acid (3) were isolated from the stem bark of Picea glehni, together with seven known diterpenoids-13-epimanoyl oxide (4), dehydroabietic acid (5), (11E)-14, 15-bisnor-8alpha-hydroxy-11-labden-13-one (6), abieta-8,11, 13-trien-7-one (7), 9alpha,13alpha-epidioxyabiet-8(14)-en-18-oic acid (8), 9,10alpha-epoxy-9,10-seco-abieta-8,11,13-trien-18-oic acid (9), and methyl 15-hydroxy-7-oxo-dehydroabietate (10). Compounds 5-8 and 10 showed potent inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol 13-acetate.     

Tyrosinase inhibitory pentacyclic triterpenes and analgesic and spasmolytic activities of methanol extracts of Rhododendron collettianum

During the course of screening of medicinal plants of Pakistan for the isolation and structure elucidation of bioactive natural products, it was found that the methanol extract of the Rhododendron collettianum showed analgesic and spasmolytic activities. The methanol extract was then extracted with chloroform. Nine pentacyclic triterpenes were isolated from the chloroform extract and their structures were elucidated as erythrodiol (1), betulinic acid (2), maslinic acid (3), 2alpha,3alpha,23-trihydroxyolean-12-en-28-oic acid (4), bayogenin (5), arjunilic acid (6), methyl arjunolate (7), arjungenin (8) and 3beta, 23, 24-trihydroxyolean-12-en-28-oic acid (9). Among the triterpenes (1-9) tested, arjunilic acid (6) was found to be most potent. Their structure-activity relationship (SAR) showed that if the configuration of the -OH group at C-2 is changed from alpha to beta the potency is decreased. In most of the compounds the position and configuration of the -OH group was found to be important for the inhibitory potency against the enzyme tyrosinase. For the comparison, the standard tyrosinase inhibitors kojic acid (IC50=16.67 microm) and L-mimosine (IC50=3.68 microm) were used as controls.