Biological Activities of Phenolic Compounds and Triterpenoids from the Galls of Terminalia chebula

Abstract

Nine phenolic compounds, including two phenolic carboxylic acids, 1 and 2, seven hydrolyzable tannins, 3-9, eight triterpenoids, including four oleanane-type triterpene acids, 10-13, and four of their glucosides, 14-17, isolated from a MeOH extract of the gall of Terminalia chebula Retz. (myrobalan tree; Combretaceae), were evaluated for their inhibitory activities against melanogenesis in B16 melanoma cells induced by α-melanocyte-stimulating hormone (α-MSH), against the Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) in Raji cells, and against TPA-induced inflammation in mice. Their 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities and cytotoxic activities against four human cancer cell lines were also evaluated. Compounds 6-9 and 12 exhibited potent inhibitory activities against melanogenesis (39.3-66.3% melanin content) with low toxicity to the cells (74.5-105.9% cell viability) at a concentration of 10 μM. Western-blot analysis revealed that isoterchebulin (8) reduced the protein levels of MITF (=microphtalmia-associated transcription factor), tyrosinase, and TRP-1 (=tyrosine-related protein 1), mostly in a concentration-dependent manner. Eight triterpenoids, 10-17, showed potent inhibitory effects on EBV-EA induction with the IC50 values in the range of 269-363 mol ratio/32 pmol TPA, while these compounds exhibited no DPPH scavenging activities (IC50 >100 μM). On the other hand, the nine phenolic compounds, 1-9, exhibited potent radical-scavenging activities (IC50 1.4-10.9 μM) with weak inhibitory effects on EBV-EA induction (IC50 460-518 mol ratio/32 pmol TPA). The tannin 6 and seven triterpenoids, 10-16, have been shown to inhibit TPA-induced inflammation (1 μg/ear) in mice with the ID50 values in the range of 0.06-0.33 μmol/ear. Arjungenin (10) 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. Compounds 1, 2, 4, 5, 7-9, 12, and 13, against HL60 cell line, compounds 1 and 4, against AZ521 cell line, and compounds 1, 11, and 12, against SK-BR-3 cell line, showed moderate cytotoxic activities (IC50 13.9-73.2 μM).

Triterpene glycosides and other polar constituents of shea (Vitellaria paradoxa) kernels and their bioactivities

“…The anti-inflammatory activity of these compounds has been demonstrated to be closely parallel with that of the inhibition of DMBA-TPA papilloma formation in the mouse-skin model (Yasukawa et al, 1996), and hence the oleanolic acid derivatives tested in this study might be expected to possess high antitumor-promoting effect in the same animal model. The high anti-inflammatory activities of various types of triterpene acids Banno et al, 2004Banno et al, , 2006Manosroi et al, 2013) and oleanane-type triterpene glycosides (Manosroi et al, 2013;Ukiya et al, 2006Ukiya et al, , 2007 have also been observed in our previous studies.…”

Anti-melanogenic compounds in Rubus croceacanthus

“…Ellagitannins belong to a group of hydrolysable tannins and are polymers of hexahydroxydiphenolic acid, which is a dimeric form of gallic acid. It is believed that hydrolysable tannins including ellagitannins have antioxidant and anti-melanogenic activities, and the melanogenesis-inhibitory activity is due to the inhibition of the expression of MITF, followed by a decrease in the expression of tyrosinase and TRP-1 [17]. Therefore, the ellagitannins in berries may contribute to the reduction of pigmentation.…”

Evaluating the anthelmintic potential of leaf gall extracts of Terminalia chebula (Gaertn.) Retz. (Combretaceae)

“…The leaf gall of T. chebula are reported to be very rich in tannins, triterpenoids, flavonoids, essential oils, and others phenolic constituents. [5,7] It was reported that, phenolicsor tannins may interfere with energy generation of worms by uncoupling oxidative phosphorylation or they binds to the free protein of the gastrointestinal tract of the worms and lead to death.…”

“…5 Gall extracts of T. chebula have been found to possess anti-inflammatory activity, anti-bacterial, anti-tyrosinase activity, anti-cancer activity, and anti-ageing activity. 7 In this study, we have evaluated the anthelmintic potential of T. chebula leaf gall extracts and elucidate its phytochemical constituents for having knowledge on the principal components responsible for its biological activity.…”