Natural tyrosinase inhibitors from herbal plants are promising therapeutic agents for skincare and cosmetic products. Natural curcuminoids exhibit weak antityrosinase properties. The structural modification of curcumin, the major curcuminoid from Curcuma longa, gave 14 analogues. The tyrosinase inhibitory activity of the natural curcuminoids and the modified analogues on both L-tyrosine and DOPA substrates were evaluated. The inhibition kinetics were also undertaken. For analogues with potent activity on the L-tyrosine substrate, the isoxazole analogue 12 and two reduced analogues, hexahydrocurcumin (16) and the α,β-unsaturated analogue 17, showed IC₅₀ values of 8.3, 14.6 and 9.4 µM, and were 20.9-, 11.9- and 18.4-fold more active, respectively, than kojic acid, the reference compound. For the analogues with potent antityrosinase on DOPA substrate, the dimethylated analogue 5 exhibited the strongest antityrosinase activity against the DOPA substrate, with the IC₅₀ value of 8.0 µM, which was 16.6-fold more active than kojic acid. The inhibition kinetics revealed that curcuminoid 5 could bind with both free enzyme and with the enzyme–substrate complex. It acted as a competitive–uncompetitive mixed-II type inhibitor. Curcuminoid 17 could bind with both free enzyme and the enzyme–substrate complex. The results indicated that 17 acted as a competitive–uncompetitive mixed-I type inhibitor, while curcuminoid 12 was a noncompetitive inhibitor which bound with both free enzymes and the enzyme–substrate complex. These potent analogues might serve as new potential tyrosinase inhibitors for the prevention and treatment of skin pigmentation disorders.

The ability of oil supplementation to inhibit various metabolic syndromes has been recognized. However, there are currently no studies determining the effects of oil supplements on healthy conditions. Plukenetia volubilis L., also known as Sacha inchi, is a seed rich in essential unsaturated fatty acids that improves metabolic syndrome diseases, such as obesity and nonalcoholic fatty liver. However, the health benefits and effects of Sacha inchi oil (SIO) supplementation remain unclear. This study aims to evaluate the chemical effects and properties of Sacha inchi oil. The results of the chemical compound analysis showed that Sacha inchi is an abundant source of ω-3 fatty acids, with a content of 44.73%, and exhibits scavenging activity of 240.53 ± 11.74 and 272.41 ± 6.95 µg Trolox/g, determined via DPPH and ABTS assays, respectively, while both olive and lard oils exhibited lower scavenging activities compared with Sacha inchi. Regarding liver histology, rats given Sacha inchi supplements showed lower TG accumulation and fat droplet distribution in the liver than those given lard supplements, with fat areas of approximately 14.19 ± 6.49% and 8.15 ± 2.40%, respectively. In conclusion, our findings suggest that Sacha inchi oil is a plant source of ω-3 fatty acids and antioxidants and does not induce fatty liver and pathology in the kidney, pancreas, and spleen. Therefore, it has the potential to be used as a dietary supplement to improve metabolic syndrome diseases.

Tabernaemontana is one of the genera that is used in Chinese, Ayurvedic and Thai traditional medicine for the treatment several diseases. From a chemical point of view, the great majority of Tabernaemontana species have already been subjected to isolation and identification of indole alkaloids present in their several parts. Many of indole alkaloids have been shown to exhibit a wide array of biological activities. The biogenesis, classification and biological activities of the indole alkaloids found in Tabernaemontana species were discussed in this review and its brings the research up-to-date on the bioactive compounds produced by Tabernaemontana species, directly or indirectly related to human health.

An infection of pathogenic microorganisms can create a big problem for human health. This has triggered the need for discovery and development of antibiotic drugs with altered modes of action. Approximately 45% of antibiotic drugs are derived from Streptomyces, which are the most commonly isolated actinomycete genera. The present investigation aimed to search for and study antimicrobial-producing actinomycetes isolated from soil samples from Sammuk Mountain, Chonburi province, Thailand. A total of 50 isolates from six soil samples were obtained and their actinomycetes were better isolated using humic acid-vitamin agar medium (64.0%) than starch casein nitrate agar medium (36.0%). In addition, the secondary metabolites produced from 13 isolates (26.0%) exhibited a broad spectrum of antimicrobial activity against Gram-positive bacteria and yeast. Thus, Sammuk Mountain soil is an important source of antibiotic-producing actinomycetes.