Antityrosinase, Antioxidant, and Cytotoxic Activities of Phytochemical Constituents from Manilkara zapota L. Bark.

Hyperpigmentation is considered by many to be a beauty problem and is responsible for photoaging. To treat this skin condition, medicinal cosmetics containing tyrosinase inhibitors are used, resulting in skin whitening. In this study, taraxerol methyl ether (1), spinasterol (2), 6-hydroxyflavanone (3), (+)-dihydrokaempferol (4), 3,4-dihydroxybenzoic acid (5), taraxerol (6), taraxerone (7), and lupeol acetate (8) were isolated from Manilkara zapota bark. Their chemical structures were elucidated by analysis of their nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) data, and by comparing them with data found in the literature. The in vitro antityrosinase, antioxidant, and cytotoxic activities of the isolated compounds (1-8) were evaluated. (+)-Dihydrokaempferol (4) exhibited higher monophenolase inhibitory activity than both kojic acid and α-arbutin. However, it showed diphenolase inhibitory activity similar to kojic acid. (+)-Dihydrokaempferol (4) was a competitive inhibitor of both monophenolase and diphenolase activities. It exhibited the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and ferric reducing antioxidant power (FRAP) activities of the isolated compounds. Furthermore, (+)-dihydrokaempferol (4) also demonstrated potent cytotoxicity in breast carcinoma cell line (BT474), lung bronchus carcinoma cell line (Chago-K1), liver carcinoma cell line (HepG2), gastric carcinoma cell line (KATO-III), and colon carcinoma cell line (SW620). These results suggest that M. zapota bark might be a good potential source of antioxidants and tyrosinase inhibitors for applications in cosmeceutical products.

In vitro antioxidant and antityrosinase activities of Manilkara kauki.

Manilkara kauki L. Dubard is a tropical plant in the genus Manilkara of family Sapotaceae. This study investigated the total phenolic and flavonoid contents, and antioxidant and antityrosinase activities in different parts of M. kauki (fruits, leaves, seeds, stem barks and woods) and in fractions of stem barks. The total phenolic and flavonoid contents of the methanol and aqueous crude extracts of different parts of M. kauki ranged from 10.87 to 176.56 mg GAE (gallic acid equivalents) per gram of crude extract and 14.33 to 821.67 mg QE (quercetin equivalents) per gram of crude extract, resp. Leaves and stem barks exhibited higher total phenolic and flavonoid contents and antioxidant and anti-tyrosinase activities than fruits, seeds and woods. Stem barks were sequentially extracted with n-hexane, ethyl acetate, methanol and water and then the fractionated extracts were subjected to antioxidant and antityrosinase activities testing. The ethyl acetate and methanol extracts of stem barks exhibited higher total phenolic and flavonoid contents and antioxidant and antityrosinase activities than the n-hexane and aqueous extracts. Moreover, ethyl acetate extract of M. kauki stem exhibited the highest antityrosinase activity. It may be a potential source of tyrosinase inhibitors for pharmaceutical and cosmetic applications.

Quantitative thin layer chromatographic analysis of the saponins in tea seed meal.

INTRODUCTION: The defatted seed meal of Camellia oleifera Abel., which contains saponins, is used extensively in aquaculture to eliminate unwanted fish and harmful insects during the cultivation of prawns, and as a molluscicide to control Pomacea canaliculata Lamarck. For the quality control of such tea seed meal products, a method for the determination of saponin content is required. OBJECTIVE: To develop a simple, sensitive and specific method for the quantitative determination of saponins in tea seed meal using high-performance thin layer chromatography and densitometry. METHODOLOGY: Powdered tea seed meal samples were extracted with methanol, filtered, evaporated to dryness and the residue taken up in methanol. Samples, together with methanolic solutions of saponin standard, were analysed by HPTLC on silica gel layers eluted with ethyl acetate:methanol:water (6:3:1.5, v/v/v) and detected at 214 nm. The amounts of saponins were determined from the respective calibration curves obtained by plotting the concentrations of saponin standard against peak area. RESULTS: Tea saponin peaks were detected at about R(f )0.40. Good linearity was observed in the range of 0.9-22.2 microg/spot with a correlation coefficient of 0.9978. The limits of detection and quantification were 0.87 and 2.90 microg/spot, respectively. The content of tea saponins in 10 tested samples was found to be between 13.1 and 21.1% w/w. CONCLUSION: The assay proved to be a specific, sensitive and inexpensive method for the quality control of saponins in tea seed meal.

Molecular design and biological activities of NF-kappaB inhibitors.

NF-kappaB is a transcription factor that induces inflammatory cytokines and anti-apoptotic proteins. We designed a new NF-kappaB inhibitor that is based on the structe of the antibiotic epoxyquinomicin C. The designed compound, dehydroxymethyl-epoxyquinomicin (DHMEQ), inhibited the TNF-alpha-induced activation of NF-kappaB, and showed an anti-arthritic effect in mice. Recently, we looked into its mechanism of inhibition. DHMEQ inhibited the TNF-alpha-induced cellular DNA binding of nuclear NF-kappaB, but not the phosphorylation or degradation of I-kappaB. Moreover, DHMEQ inhibited the TNF-alpha-induced nuclear accumulation of p65, a component of NF-kappaB. On the other hand, DHMEQ did not inhibit the nuclear transport of Smad2 and the large T antigen. Also, it did not inhibit the TNF-alpha-induced activation of JNK, but synergistically induced apoptosis with TNF-alpha in human T cell leukemia Jurkat cells. Therefore, DHMEQ specifically inhibited the NF-kappaB-activating pathway in the TNF-alpha-treated cells. Taken together, our data show that DHMEQ is a unique inhibitor of NF-kappaB that acts at the level of the nuclear translocation. It may be useful as an anti-inflammatory and anticancer agent.

Synthesis and structure-activity relationship of dehydroxymethylepoxyquinomicin analogues as inhibitors of NF-kappaB functions.

We previously found dehydroxymethylepoxyquinomicin (DHMEQ) inhibited NF-kappaB activation and showed anti-inflammatory activity in vivo. Here we designed and synthesized analogues of DHMEQ and tested their biological activity as NF-kappaB inhibitors in human T cell leukemia Jurkat cells. The hydroxyl group at the 2-position of the benzamide moiety was found to be essential for the inhibitory activity. But etherification of this group did not diminish the activity completely. Thus, for further mechanistic studies the hydroxyl group at the 2-position may be useful for extension with a linker and biotin moiety.