The active component screening of Anoectochilus roxburghii and the functional study on inhibition of melanogenesis in zebrafish.

The aim of this study is to explore the active components of Anoectochilus roxburghii capable of inhibiting melanin formation using chemical separation and extraction and functional analysis. Anoectochilus roxburghii were extracted with alcohol and separated into three groups: the total extraction group, alcohol extracted group and alcohol precipitated group. Zebrafish embryos at 0.75 h post-fertilization were exposed to various concentrations of the three groups of extracts, and analyzed at 72 h, using semi-quantitative RT-PCR and in situ hybridization. The results showed that the alcohol extracts inhibit melanogenesis most significantly in the zebrafish embryos. The mRNAs of melanin-related genes, such as silv, tyr, tyrp1a, were down-regulated by the alcohol extracts spatially and temporally. The alcohol extracts also inhibited the activity of tyrosinase, a key enzyme in melanogenesis, in a dosage dependent manner. In addition, the alcohol extracts also display a remarkable inhibitory effect on melanin synthesis through down-regulation of mRNAs of melanin-related genes and tyrosinase activity in zebrafish embryos, in which a large amount of melanin has already been synthesized. Such inhibitory effect could be reversed after the withdrawal of the alcohol extracts. Our results showed that the alcohol extracts of Anoectochilus roxburghii can significantly inhibit zebrafish melanogenesis, supporting the notion that Anoectochilus roxburghii could potentially be used in the development and production of natural whitening products.

Three new 2,5-diketopiperazines from the fish intestinal Streptomyces sp. MNU FJ-36.

The gut actinobacteria of marine-inhabited fish is one of the most important reservoirs of novel natural products. Currently, the Streptomyces sp. MNU FJ-36 was isolated from the intestinal fabric of Katsuwonus sp. and determined by 16S rRNA analysis. From the cultures of the S. sp. MNU FJ-36, three new 2,5-diketopiperazines (2,5-DKPs) were discovered and identified as 3-(3-hydroxy-4-methoxybenzyl)-6-isobutyl-2,5-diketopiperazine (1), 3-(1,3-benzodioxol-5-ylmethyl)-6-isobutyl-2,5-diketopiperazine (2) and 3-(1,3-benzodioxol-5-ylmethyl)-6-isopropyl-2,5-diketopiperazine (3). Their structures were elucidated on the basis of spectroscopic data analysis. All the compounds were also evaluated for their inhibitory activity against P388, A-549 and HCT-116 cell lines with the MTT assay.

Guanacastane-type diterpenoids from Coprinus radians.

Thirteen diterpenoids, named radianspenes A-M (1-13), including three lactams radianspenes J (10), K (11) and L (12) and one dimer radianspene M (13), were isolated from fermentation products of the higher fungal strain Coprinus radians M65. All these compounds possessing guanacastane skeleton were evaluated for antitumor activity using MDA-MB-435 cell line. Radianspene C exhibited inhibitory activity with IC(50) of 0.91 µM.