Cancer Chemopreventive Effect of Bergenin from Peltophorum pterocarpum Wood

The aqueous extract of Peltophorum pterocarpum (Fabaceae) wood exhibited potent inhibitory effects against Epstein? Barr virus early antigen (EBV‐EA) activation induced with 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in Raji cells and against melanogenesis in α‐melanocyte‐stimulating hormone (α‐MSH)‐stimulated B16 melanoma cells, as well as potent 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) free radical‐scavenging activity. Two phenolic acid derivatives, bergenin ( 1 ) and gallic acid ( 2 ), were isolated from the ethyl acetate (AcOEt)‐soluble fraction obtained from the extract. Compound 1 exhibited potent inhibitory effect against EBV‐EA activation and against skin tumor promotion in an in vivo two‐stage mouse skin carcinogenesis test based on 7,12‐dimethylbenz[a]anthracene (DMBA) as initiator, and with TPA as promoter. Both compounds 1 and 2 exhibited melanogenesis‐inhibitory activities in α‐MSH‐stimulated B16 melanoma cells, and, in addition, compound 2 showed strong DPPH radical‐scavenging activity.     

Melanogenesis‐Inhibitory and Cytotoxic Activities of Limonoids,Alkaloids, and Phenolic Compounds from Phellodendron amurense Bark

Four limonoids, 1  –  4 , five alkaloids, 5  –  9 , and four phenolic compounds, 10  –  13 , were isolated from a MeOH extract of the bark of Phellodendron amurense (Rutaceae). Among these, compound 13 was new, and its structure was established as rel‐(1R,2R,3R)‐5‐hydroxy‐3‐(4‐hydroxy‐3‐methoxyphenyl)‐6‐methoxy‐1‐(methoxycarbonylmethyl)indane‐2‐carboxylic acid methyl ester (γ‐di(methyl ferulate)) based on the spectrometric analysis. Upon evaluation of compounds 1  –  13 against the melanogenesis in the B16 melanoma cells induced with α‐melanocyte‐stimulating hormone (α‐MSH), four compounds, limonin ( 1 ), noroxyhydrastinine ( 6 ), haplopine ( 7 ), and 4‐methoxy‐1‐methylquinolin‐2(1H)‐one ( 8 ), exhibited potent melanogenesis‐inhibitory activities with almost no toxicity to the cells. Western blot analysis revealed that compound 6 inhibited melanogenesis, at least in part, by inhibiting the expression of protein levels of tyrosinase, TRP‐1, and TRP‐2 in α‐MSH‐stimulated B16 melanoma cells. In addition, when compounds 1  –  13 were evaluated for their cytotoxic activities against leukemia (HL60), lung (A549), duodenum (AZ521), and breast (SK‐BR‐3) cancer cell lines, five compounds, berberine ( 5 ), 8 , canthin‐6‐one ( 9 ), α‐di‐(methyl ferulate) ( 12 ), and 13 , exhibited cytotoxicities against one or more cancer cell lines with IC₅₀ values in the range of 2.6 – 90.0 μm . In particular, compound 5 exhibited strong cytotoxicity against AZ521 (IC₅₀ 2.6 μm ) which was superior to that of the reference cisplatin (IC₅₀ 9.5 μm ).     

Glycosidic Inhibitors of Melanogenesis from Leaves of Passiflora edulis

A new flavonoid glycoside, chrysin 6‐C‐β‐rutinoside (chrysin α‐L ‐rhamnopyranosyl‐(1→6)‐C‐β‐glucopyranoside; 2 ), and two new triterpene glycosides, (31R)‐31‐O‐methylpassiflorine ( 7 ) and (31S)‐31‐O‐methylpassiflorine ( 8 ), along with 14 known glycosides, including three flavonoid glycosides, 1, 3 , and 4 , six triterpene glycosides, 5, 6 , and 9 – 12 , three cyano glycosides, 13 – 15 , and two other glycosides, 16 and 17 , were isolated from a MeOH extract of the leaves of Passiflora edulis (passion flower; Passifloraceae). The structures of new compounds were elucidated on the basis of extensive spectroscopic analysis and comparison with literature data. Upon evaluation of compounds 1 – 17 against the melanogenesis in the B16 melanoma cells induced with α‐melanocyte‐stimulating hormone (α‐MSH), three compounds, isoorientin ( 1 ), 2 , and (6S,9R)‐roseoside ( 17 ), exhibited inhibitory effects with 37.3–47.2% reduction of melanin content with no, or almost no, toxicity to the cells (90.8–100.2% cell viability) at 100 μM . Western blot analysis showed that compound 2 reduced the protein levels of MITF, TRP‐1, and tyrosinase, in a concentration‐dependent manner while exerted almost no influence on the level of TRP‐2, suggesting that this compound inhibits melanogenesis on the α‐MSH‐stimulated B16 melanoma cells by, at least in part, inhibiting the expression of MITF, followed by decreasing the expression of TRP‐1 and tyrosinase. In addition, compounds 1 – 17 were evaluated for their inhibitory effects against the Epstein? Barr virus early antigen (EBV‐EA) activation induced by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in Raji cells.     

Melanogenesis‐Inhibitory and Cytotoxic Activities of Chemical Constituents from the Leaves of Sauropus androgynus L. Merr. (Euphorbiaceae)

A new steroid, 20‐hydroxyisofucosterol (stigmasta‐5,24(28)‐diene‐3β,20β‐diol) ( 7 ), along with six known compounds 1 – 6 were isolated from the MeOH extract of the leaves of Sauropus androgynus L. Merr . (Euphorbiaceae). The structure of new steroid was determined by HR‐APCI‐MS and various NMR techniques in combination with literature data. Subsequently, their anti‐inflammatory, cytotoxic activities against five human cell lines, as well as inhibitory activities against the α‐MSH induced melanogenesis on the B16 cell line were evaluated. As the results, steroid compounds, 6 and 7 exhibited moderate cytotoxic to HL60, AZ521, SKBR3, and A549 tumor cell lines (IC₅₀ 26.9 – 45.1 μm ) with high tumor selectivity for A549 relative to WI38 cell lines (SI 2.6 and 3.0, resp.). And, flavonoid compounds, 4 and 5 exhibited superior inhibitory activities against melanogenesis (67.0 – 94.7% melanin content), even with no or low toxicity to the cells (90.1 – 99.6% cell viability) at the concentrations from 10 to 100 μm . Furthermore, Western blot analysis suggested that compound 5 could inhibit melanogenesis by suppressing the protein expressions of MITF, TRP‐1, TRP‐2, and tyrosinase.     

Melanogenesis‐Inhibitory Saccharide Fatty Acid Esters and Other Constituents of the Fruits of Morinda citrifolia (Noni)

Five new saccharide fatty acid esters, named nonioside P ( 3 ), nonioside Q ( 4 ), nonioside R ( 8 ), nonioside S ( 10 ), and nonioside T ( 14 ), and one new succinic acid ester, butyl 2‐hydroxysuccinate (=4‐butoxy‐3‐hydroxy‐4‐oxobutanoic acid) ( 31 ), were isolated, along with 26 known compounds, including eight saccharide fatty acid esters, 1, 2, 5, 6, 7, 9, 12 , and 13 , three hemiterpene glycosides, 15, 17 , and 18 , six iridoid glycosides, 21 – 25 , and 27 , and nine other compounds, 20, 28, 29 , and 32 – 37 , from a MeOH extract of the fruit of Morinda citrifolia (noni). Upon evaluation of these and five other glycosidic compounds, 11, 16, 19, 26 , and 30 , from M. citrifolia fruit extract for their inhibitory activities against melanogenesis in B16 melanoma cells induced with α‐melanocyte‐stimulating hormone (α‐MSH), most of the saccharide fatty acid esters, hemiterpene glycosides, and iridoid glycosides showed inhibitory effects with no or almost no toxicity to the cells. These compounds were further evaluated with respect to their cytotoxic activities against two human cancer cell lines (HL‐60 and AZ521) and their inhibitory effects on Epstein? Barr virus early antigen (EBV‐EA) activation induced with 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in Raji cells.     

Biological Activities of Phenolics from the Fruits of Phyllanthus emblica L. (Euphorbiaceae)

Seven phenolic compounds, 1 – 7 , including a new organic acid gallate, mucic acid 1‐ethyl 6‐methyl ester 2‐O‐gallate ( 7 ), were isolated from the MeOH extract of the fruits of Phyllanthus emblica L. (Euphorbiaceae). The structures were elucidated on the basis of extensive spectroscopic analysis and comparison with literature data. Upon evaluated for their antioxidant abilities by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), 2,2′‐azinobis(3‐ethylbenzthiazoline‐6‐sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) assays. The inhibitory activities against melanogenesis in B16 melanoma cells induced by α‐MSH, as well as cytotoxic activities against four human cancer cell lines were also evaluated. All phenolic compounds, 1 – 7 , exhibited potent antioxidant abilities (DPPH: IC₅₀ 5.6 – 12.9 μm ; ABTS: 0.87 – 8.43 μm Trolox/μm ; FRAP: 1.01 – 5.79 μm Fe²⁺/μm , respectively). Besides, 5 – 7 , also exhibited moderate inhibitory activities against melanogenesis (80.7 – 86.8% melanin content), even with no or low toxicity to the cells (93.5 – 101.6% cell viability) at a high concentration of 100 μm . Compounds 1 – 3 exhibited cytotoxic activity against one or more cell lines (IC₅₀ 13.9 – 68.4%), and compound 1 with high tumor selectivity for A549 (SI 3.2).     

Cytotoxic and Melanogenesis‐Inhibitory Activities of Limonoids from the Leaves of Azadirachta indica (Neem)

Seventeen limonoids (tetranortriterpenoids), 1 – 17 , including three new compounds, i.e., 17‐defurano‐17‐(2,5‐dihydro‐2‐oxofuran‐3‐yl)‐28‐deoxonimbolide ( 14 ), 17‐defurano‐17‐(2ξ‐2,5‐dihydro‐2‐hydroxy‐5‐oxofuran‐3‐yl)‐28‐deoxonimbolide ( 15 ), and 17‐defurano‐17‐(5ξ‐2,5‐dihydro‐5‐hydroxy‐2‐oxofuran‐3‐yl)‐2′,3′‐dehydrosalannol ( 17 ), were isolated from an EtOH extract of the leaf of neem (Azadirachta indica). The structures of the new compounds were elucidated on the basis of extensive spectroscopic analyses and comparison with literature. Upon evaluation of the cytotoxic activities of these compounds against leukemia (HL60), lung (A549), stomach (AZ521), and breast (SK‐BR‐3) cancer cell lines, seven compounds, i.e., 1 – 3, 12, 13, 15 , and 16 , exhibited potent cytotoxicities with IC₅₀ values in the range of 0.1–9.9 μM against one or more cell lines. Among these compounds, cytotoxicity of nimonol ( 1 ; IC₅₀ 2.8 μM ) against HL60 cells was demonstrated to be mainly due to the induction of apoptosis by flow cytometry. Western blot analysis suggested that compound 1 induced apoptosis via both the mitochondrial and death receptor‐mediated pathways in HL60 cells. In addition, when compounds 1 – 17 were evaluated for their inhibitory activities against melanogenesis in B16 melanoma cells, induced with α‐melanocyte‐stimulating hormone (α‐MSH), seven compounds, 1, 2, 4 – 6, 15 , and 16 , exhibited inhibitory activities with 31–94% reduction of melanin content at 10 μM concentration with no or low toxicity to the cells (82–112% of cell viability at 10 μM ). All 17 compounds were further evaluated for their inhibitory effects against the Epstein? Barr virus early antigen (EBV‐EA) activation induced by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in Raji cells.     

Anti-inflammatory and anti-tumor-promoting effects of 5-deprenyllupulonol C and other compounds from Hop (Humulus lupulus L.)

A new phloroglucinol derivative, 5‐deprenyllupulonol C ( 1 ), along with four other phloroglucinol derivatives, 2 – 5 , five chalcones, 6 – 10 , four flavanones, 11 – 14 , two flavonol glycosides, 15 and 16 , and five triterpenoids, 17 – 21 , were isolated from the female inflorescence pellet extracts of hop (Humulus lupulus L.). Upon evaluation of these compounds against the Epstein? Barr virus early antigen (EBV‐EA) activation induced by 12‐O‐tetradecanoylphorbol 13‐acetate (TPA) in Raji cells, twelve compounds, i.e., 1 – 4, 11 – 14, 17 – 19 , and 21 , showed potent inhibitory effects on EBV‐EA induction, with IC₅₀ values in the range of 215–393 mol ratio/32 pmol TPA. In addition, eleven compounds, i.e., 1 – 4, 6, 11, 12, 14, 17, 18 , and 20 , were found to inhibit TPA‐induced inflammation (1 μg/ear) in mice, with ID₅₀ values in the range of 0.13–1.06 μmol per ear. Further, lupulone C ( 2 ) and 6‐prenylnaringenin ( 14 ) exhibited inhibitory effects on skin‐tumor promotion in an in vivo two‐stage mouse‐skin carcinogenesis test based on 7,12‐dimethylbenz[a]anthracene (DMBA) as initiator and with TPA as promoter.     

A novel synthetic Piper amide derivative NED‐180 inhibits hyperpigmentation by activating the PI3K and ERK pathways and by regulating Ca2+ influx via TRPM1 channels

Piper amides have a characteristic, unsaturated amide group and exhibit diverse biological activities, including proliferation and differentiation of melanocytes, although the molecular mechanisms underlying its antimelanogenesis effect remain unknown. We screened a selected chemical library of newly synthesized Piper amide derivatives and identified (E)‐3‐(4‐(tert‐butyl)phenyl)‐N‐(2,3‐dihydrobenzo[b][1,4]dioxin‐6‐yl)acrylamide (NED‐180) as one of the most potent compounds in suppressing melanogenesis. In murine melan‐a melanocytes, NED‐180 downregulated the expression of melanogenic regulatory proteins including tyrosinase, Tyrp1, Dct, and MITF. PI3K/Akt‐dependent phosphorylation of GSK3β by NED‐180 decreases MITF phosphorylation and inhibits melanogenesis without any effects on cytotoxicity and proliferation. Furthermore, topical application of NED‐180 significantly ameliorated UVB‐induced skin hyperpigmentation in guinea pigs. Interestingly, data obtained using calcium imaging techniques suggested that NED‐180 reduced the TPA‐induced activation of TRPM1 (melastatin), which could explain the NED‐180‐induced inhibition of melanogenesis. All things taken together, NED‐180 triggers activation of multiple pathways, such as PI3K and ERK, and inhibits TRPM1/TRPV1, leading to inhibition of melanogenesis.     

Limonoids and Flavonoids from the Flowers of Azadirachta indica var. siamensis,and Their Melanogenesis‐Inhibitory and Cytotoxic Activities

A new limonoid, 7‐O‐acetyl‐7‐O‐debenzoyl‐22‐hydroxy‐21‐methoxylimocinin ( 2 ), and two new flavonoids, 3′‐(3‐hydroxy‐3‐methylbutyl)naringenin ( 7 ) and 4′‐O‐methyllespedezaflavanone C ( 9 ), along with nine known compounds, including two limonoids, 1 and 3 , and seven flavonoids, 4 – 6, 8 , and 10 – 12 , were isolated from a MeOH extract of the flowers of Azadirachta indica A.Juss. var. siamensis Valeton (Siamese neem tree; Meliaceae). The structures of new compounds were elucidated on the basis of extensive spectroscopic analysis and comparison with literature data. All of these compounds were evaluated for their melanogenesis‐inhibitory activities in B16 melanoma cells induced with α‐melanocyte‐stimulating hormone (α‐MSH). Compound 2 (16.9% melanin content at 30 μM ), 6‐deacetylnimbin ( 3 ; 49.6% melanin content at 100 μM ), and kaempferide ( 10 ; 41.7% melanin content at 10 μM ) exhibited inhibitory effects with no, or almost no, toxicity to the cells (81.0–111.7% cell viability). In addition, evaluation of their cytotoxic activities against HL60, A549, AZ521, and SK‐BR‐3 human cancer cell lines, isoazadironolide ( 1 ), 4′‐O‐methyl‐8‐prenylnaringenin ( 5 ), euchrestaflavanone A ( 8 ), 9 , and 3‐methoxy‐3′‐prenylnaringenin ( 12 ) revealed potent cytotoxicities against one or more cell lines with IC₅₀ values in the range of 4.5–9.9 μM .     

Antitumor‐Promoting Effects and Cytotoxic Activities of Dammar Resin Triterpenoids and Their Derivatives

Nineteen known triterpenoids, 1 – 19 , and one known sesquiterpenoid, 20 , were isolated from dammar resin obtained from Shorea javanica K. & V. (Dipterocarpaceae). One of the acidic triterpenoids, dammarenolic acid ( 1 ), was converted to fourteen derivatives, namely, an alcohol, 21 , an aldehyde, 22 , and twelve L ‐amino acid conjugates, 23 – 34 . Compounds 1 – 34 were examined for their inhibitory effects on the induction of Epstein–Barr virus early antigen (EBV‐EA) by 12‐O‐tetradecanoylphorbol 13‐acetate (TPA) in Raji cells, a known primary screening test for antitumor promoters. All of the compounds tested, except for compounds 4, 5, 12 – 14, 16 , and 17 , showed inhibitory effects against EBV‐EA activation with potencies either comparable with or stronger than that of β‐carotene, a known natural antitumor promoter. In addition, (20S)‐20‐hydroxy‐3,4‐secodammara‐4(28),24‐dien‐3‐al ( 22 ) exhibited inhibitory effects on skin tumor promotion in an in vivo two‐stage mouse skin carcinogenesis test based on 7,12‐dimethylbenz[a]anthracene (DMBA) as initiator, and with TPA as promoter. Furthermore, evaluation of the cytotoxic activities of compounds 1 – 34 against human cancer cell lines showed that reduction (i.e., 21 and 22 ) or conjugation with L ‐amino acids (i.e., 23 – 34 ) of compound 1 enhanced the cytotoxicity against human melanoma cell line CRL1579.     

Melanogenesis‐Inhibitory Activities of Isomeric C‐seco Limonoids and Deesterified Limonoids

Treatment of eight C‐seco limonoids including six of salannin‐type, 1 – 6 , and two of nimbin‐type, 7 and 8 , with a combination of BF₃ · Et₂O and iodide ion yielded the isomeric C‐seco derivatives, i.e., six isosalannins, 1a – 6a , and two isonimbins, 7a and 8a , respectively. Ohchinin ( 1 ) was further subjected to LiAlH₄ reduction which yielded a deesterified trihydroxy limonoid, nimbidinol ( 9 ). In addition, ten limonoids including seven of azadirone‐type, 10 – 16 , and three of gedunin‐type, 17 – 19 , all of which possess no ester functionality in the molecule, were obtained from the neutral fraction of Azadirachta indica seed extract after alkaline hydrolysis. Among the above, twelve compounds, i.e., 1a – 4a , 6a , 9 , 13 – 16 , 18 , and 19 , were new compounds, and their structures were elucidated on the basis of extensive spectroscopic analysis and comparison with literature data. Upon evaluation of all these limonoids for their inhibitory activities against melanogenesis in B16 melanoma cells induced with α‐melanocyte‐stimulating hormone (α‐MSH), five structurally modified limonoids, 3‐deacetyl‐28‐oxosalannin ( 6a ), 9 , 17‐epi‐17‐hydroxynimbocinol ( 14 ), 17‐epi‐17‐hydroxy‐15‐methoxynimbocinol ( 15 ), and 7‐deacetyl‐17‐epinimolicinol ( 18 ), in addition to a natural limonoid, 1 , exhibited potent inhibitory activities with 26 – 66% reduction of melanin content at 100 μm concentration with almost no or low toxicity to the B16 melanoma cells (70 – 99% cell viability at 100 μm ).     

Cytotoxic Activities and Anti‐Tumor‐Promoting Effects of Microbial Transformation Products of Prenylated Chalcones from Angelica keiskei

Three prenylated chalcones, 4‐hydroxyderricin ( 1 ), xanthoangelol ( 2 ), and xanthoangelol F ( 3 ), isolated from Angelica keiskei, were transformed by the fungus Aspergillus saitoi. These chalcones were converted to flavanones (i.e., 4, 8 , and 12 ), and prenyl‐chain‐hydrated (i.e., 5, 7, 9 – 11 , and 13 ) and ring‐B‐hydroxylated (i.e., 6 ) chalcones. The structures of three new metabolites, 7, 9 , and 13 , were established as 2″,3″‐dihydro‐4,3″‐dihydroxyderricin, 6″,7″‐dihydro‐7″‐hydroxyxanthoangelol, and 6″,7″‐dihydro‐7″‐hydroxyxanthoangelol F, respectively. Upon evaluation of cytotoxic activities of compounds 1 – 13 , the metabolite 7 exhibited potent cytotoxicity against HL60 cells, and this cell death was revealed to be mostly due to apoptosis. In addition, compounds 1 – 4, 7 – 10, 12 , and 13 were examined for their inhibitory effects on the induction of Epstein? Barr virus early antigen (EBV‐EA) by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in Raji cells. All compounds tested showed inhibitory effects against EBV‐EA activation with potencies higher than that of β‐carotene. Furthermore, the metabolite 13 exhibited inhibitory effect on skin tumor promotion in an in vivo two‐stage mouse skin carcinogenesis test based on 7,12‐dimethylbenz[a]anthracene (DMBA) as initiator, and with TPA as promoter.     

IFN‐γ inhibits basal and α‐MSH‐induced melanogenesis

Inflammatory cytokines are closely related to pigmentary changes. In this study, the effects of IFN‐γ on melanogenesis were investigated. IFN‐γ inhibits basal and α‐MSH‐induced melanogenesis in B16 melanoma cells and normal human melanocytes. MITF mRNA and protein expressions were significantly inhibited in response to IFN‐γ. IFN‐γ inhibited CREB binding to the MITF promoter but did not affect CREB phosphorylation. Instead, IFN‐γ inhibited the association of CBP and CREB through the increased association between CREB binding protein (CBP) and STAT1. These findings suggest that IFN‐γ inhibits both basal and α‐MSH‐induced melanogenesis by inhibiting MITF expression. The inhibitory action of IFN‐γ in α‐MSH‐induced melanogenesis is likely to be associated with the sequestration of CBP via the association between CBP and STAT1. These data suggest that IFN‐γ plays a role in controlling inflammation‐ or UV‐induced pigmentary changes.     

Cytotoxic and Nitric Oxide Production‐Inhibitory Activities of Limonoids and Other Compounds from the Leaves and Bark of Melia azedarach

Nine limonoids, 1 – 9 , one apocarotenoid, 11 , one alkaloid, 12 , and one steroid, 13 , from the leaf extract; and one triterpenoid, 10 , five steroids, 14 – 18 , and two flavonoids, 19 and 20 , from the bark extract of Melia azedarach L. (Chinaberry tree; Meliaceae) were isolated. Among these compounds, three compounds, 4 – 6 , were new, and their structures were established as 3‐deacetyl‐28‐oxosalannolactone, 3‐deacetyl‐28‐oxosalanninolide, and 3‐deacetyl‐17‐defurano‐17,28‐dioxosalannin, respectively, on the basis of extensive spectroscopic analyses and comparison with literature data. All of the isolated compounds were evaluated for their cytotoxic activities against leukemia (HL60), lung (A549), stomach (AZ521), and breast (SK‐BR‐3) cancer cell lines. 3‐Deacetyl‐4′‐demethyl‐28‐oxosalannin ( 3 ) against HL60 and AZ521 cells, and methyl kulonate ( 10 ) against HL60 cells exhibited potent cytotoxicities with IC₅₀ values in the range of 2.8–5.8 μM . In addition, upon evaluation of compounds 1 – 13 against production of nitric oxide (NO) in mouse macrophage RAW 264.7 cells induced by lipopolysaccharide (LPS), seven, i.e., trichilinin B ( 1 ), 4 , ohchinin ( 7 ), 23‐hydroxyohchininolide ( 8 ), 21‐hydroxyisoohchininolide ( 9 ), 10 , and methyl indole 3‐carboxylate ( 12 ), inhibited production of NO with IC₅₀ values in the range of 4.6–87.3 μM with no, or almost no, toxicity to the cells (IC₅₀ 93.2–100 μM ). Western blot analysis revealed that compound 7 reduced the expression levels of the inducible NO synthase (iNOS) and COX‐2 proteins in a concentration‐dependent manner. Furthermore, compounds 5, 6, 13 , and 18 – 20 exhibited potent inhibitory effects (IC₅₀ 299–381 molar ratio/32 pmol TPA) against Epstein? Barr virus early antigen (EBV‐EA) activation induced by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in Raji cell line.