Gamma-pyrone derivatives, kojic acid methyl ethers from a marine-derived fungus Alternaria [correction of Altenaria] sp.

Kojic acid dimethyl ether (1), and the known kojic acid monomethyl ether (2), kojic acid (3) and phomaligol A (4) have been isolated from the organic extract of the broth of the marine-derived fungus Alternaria sp. collected from the surface of the marine green alga Ulva pertusa. The structures were assigned on the basis of comprehensive spectroscopic analyses. Each isolate was tested for its tyrosinase inhibitory activity. Kojic acid (3) was found to have significant tyrosinase inhibitory activity, but compounds 1, 2, and 4 were found to be inactive.

Inhibitory effects of Ramulus mori extracts on melanogenesis.

To develop an active agent for skin whitening, the inhibitory effects of 285 plant extracts on tyrosinase activity were examined, and one plant extract having tyrosinase inhibition activity was chosen. Ramulus mori (young twigs of Morus alba L.) extracts showed inhibition activity in tyrosinase and melanin synthesis in B-16 melanoma cells. To clarify the mechanism of its inhibition on melanogenesis, the effect of R. mori extracts on tyrosinase activity, synthesis, and gene expression was evaluated. R. mori extracts showed tyrosinase inhibition activity by competitive method, and there was no suppression of tyrosinase synthesis and gene expression. Further, to evaluate the inhibitory activity of R. mori in vivo, its effect on melanin production in UV-induced brown guinea pigs was examined, where a decrease of melanin production in the guinea pig model was observed. Also, R. mori extracts showed no toxicity in animal tests such as the acute toxicity test, the skin irritation test, the eye irritation test, the skin sensitization test, and the acute oral toxicity test, and no toxicity in the human skin irritation test. A single compound from R. mori extracts was purified using various column chromatography and recrystallization, and its chemical structure was identified using mass chromatography, IR spectroscopy, and NMR analysis. The chemical structure was that of 2,3',4,5'-tetrahydroxystilbene(2-oxyresveratrol) and showed inhibition activity on tyrosinase (IC(50) = 0.23 microg/ml). Also, R. mori extracts inhibited tyrosinase activity in a competitive manner (Ki = 1.5 x 10(-6) M) when L-tyrosine was used as a substrate.

Co-culture with NK-92MI cells enhanced the anti-cancer effect of bee venom on NSCLC cells by inactivation of NF-κB.

In the present study we experimented on a multimodal therapeutic approach, such as combining chemotherapy agent (Bee venom) with cellular (NK-92MI) immunotherapy. Previously bee venom has been found to show anti-cancer effect in various cancer cell lines. In lung cancer cells bee venom showed an IC(50) value of 3 µg/ml in both cell lines. The co-culture of NK-92MI cell lines with lung cancer cells also show a decrease in viability upto 50 % at 48 h time point. Hence we used bee venom treated NK-92MI cells to co-culture with NSCLC cells and found that there is a further decrease in cell viability upto 70 and 75 % in A549 and NCI-H460 cell lines respectively. We further investigated the expression of various apoptotic and anti-apoptotic proteins and found that Bax, cleaved caspase-3 and -8 were increasing where as Bcl-2 and cIAP-2 was decreasing. The expression of various death receptor proteins like DR3, DR6 and Fas was also increasing. Concomitantly the expression of various death receptor ligands (TNFalpha, Apo3L and FasL) was also increasing of NK-92MI cells after co-culture. Further the DNA binding activity and luciferase activity of NF-κB was also inhibited after co-culture with bee venom treated NK-92MI cell lines. The knock down of death receptors with si-RNA has reversed the decrease in cell viability and NF-κB activity after co-culture with bee venom treated NK-92MI cells. Thus this new approach can enhance the anti-cancer effect of bee venom at a much lower concentration.