Methylation in hangtaimycin biosynthesis and its antibacterial activities.

About two-thirds of small molecule drugs contain methyl group and it plays a very important role in the drug development. So, methyltransferases catalyzing the methylation have always attracted great attention. Hangtaimycin (HTM) is a potent hepatoprotective agent. Previous study showed that its biosynthetic gene cluster contained three methyltransferase domains, but their characteristics in HTM biosynthetic pathway has not been revealed. In this study, we clarified multi-methylations in HTM biosynthesis in vivo. It showed that the two S-adenosylmethionine-dependent methyltransferases (SAM-MTs) of HtmA2(-module 6)-MT domain and HtmB2(-module 18)-MT domain are responsible for the installation of methyl group at C-45 and N-12, respectively, whereas the FK506 methyltransferase (FKMT) type O-methyltransferase of HtmB1(-module 16)-MT domain take care of the methylation at O-21 of HTM. We also reported the antibacterial activities of HTM in this study, and found that it showed activities against M. luteus, B. thuringiensis and A. baumannii with MIC of 4 µg/mL, 4 µg/mL, and 64 µg/mL, respectively.

A review: The nutrition components, active substances and flavonoid accumulation of Tartary buckwheat sprouts and innovative physical technology for seeds germinating.

Compared with the common grain, Tartary buckwheat enjoys higher nutritional value. Some distinctive nutrition associated with physiological activity of Tartary buckwheat is valuable in medicine. In addition, it's a good feed crop. In the paper, the main components (starch, protein, amino acid, fatty acid and mineral) and polyphenol bioactive components in Tartary buckwheat and its sprouts were reviewed, and the accumulation of flavonoids in sprouts during germination, especially the methods, synthetic pathways and mechanisms of flavonoid accumulation was summarized. The research on bioactive components and health benefits of Tartary buckwheat also were reviewed. Besides, the applications of innovative physical technology including microwave, magnetic, electromagnetic, ultrasonic, and light were also mentioned and highlighted, which could promote the enrichment of some active substances during seeds germination and growth of Tartary buckwheat sprouts. It would give a good support and benefit for the research and processing of Tartary buckwheat and its sprouts in next day.

Effects of Exogenous Caffeic Acid, L-Phenylalanine and NaCl Treatments on Main Active Components Content and In Vitro Digestion of Germinated Tartary Buckwheat.

Germination is an effective method for improving the nutritional value of Tartary buckwheat (TB). The effects of exogenous additive treatments (caffeic acid (CA), L-phenylalanine (L-Phe), NaCl) on germination, main active component contents and antioxidant activities before and after in vitro digestion of germinated TB were investigated. Compared with the natural growth group, the T4 group (CA 17 mg/L, L-Phe 2.7 mmol/L, NaCl 2.7 mmol/L) treatment increased the germination rate (67.50%), sprout length, reducing sugar (53.05%), total flavonoid (18.36%) and total phenolic (20.96%) content, and antioxidant capacity of TB. In addition, exogenous additives treatment induced the consumption of a lot of nutrients during seed germination, resulting in a decrease in the content of soluble protein and soluble sugar. The stress degree of natural germination on seeds was higher than that of low concentrations of exogenous additives, resulting in an increase in malondialdehyde content. In vitro digestion leads to a decrease in phenolics content and antioxidant capacity, which can be alleviated by exogenous treatment. The results showed that treatment with exogenous additives was a good method to increase the nutritional value of germinated TB, which provided a theoretical basis for screening suitable growth conditions for flavonoid enrichment.

Two new streptovaricin derivatives from mutants of Streptomyces spectabilis CCTCC M2017417.

Two new ansamycin derivatives, damavaricin H (1) and protostreptovaricin VI (2) were isolated from the Streptomyces spectabilis CCTCC M2017417 derived mutants of ΔstvP5 and ΔstvA2, respectively. The structures of 1 and 2 were established by analysis of the HRESIMS as well as 1D and 2D NMR datasets. The minimum inhibitory concentration (MIC) results showed that compounds 1 and 2 possessed the corresponding anti-MRSA bioactivities of 4 ∼ 8 µg/ml and 8 ∼ 16 µg/ml, which confirmed the structure-activity relationships of streptovaricins reported previously and also revealed that addition of the hydroxyl group at C-8 increased the anti-MRSA activity.

The Mechanism of Dehydrating Bimodules in trans-Acyltransferase Polyketide Biosynthesis: A Showcase Study on Hepatoprotective Hangtaimycin.

A bioassay-guided fractionation led to the isolation of hangtaimycin (HTM) from Streptomyces spectabilis CCTCC M2017417 and the discovery of its hepatoprotective properties. Structure elucidation by NMR suggested the need for a structural revision. A putative HTM degradation product was also isolated and its structure was confirmed by total synthesis. The biosynthetic gene cluster was identified and resembles a hybrid trans-AT PKS/NRPS biosynthetic machinery whose first PKS enzyme contains an internal dehydrating bimodule, which is usually found split in other trans-AT PKSs. The mechanisms of such dehydrating bimodules have often been proposed, but have never been deeply investigated. Here we present in vivo mutations and in vitro enzymatic experiments that give first and detailed mechanistic insights into catalysis by dehydrating bimodules.

Antibacterial natural products lobophorin L and M from the marine-derived Streptomyces sp. 4506.

Two new spirotetronate natural products, lobophorin L (1) and lobophorin M (2), together with three known lobophorin-like spirotetronate antibiotics (3-5) and two known ansamycins (6-7), were isolated from the marine-derived Streptomyces sp. 4506. The structures of 1 and 2 were established on the basis of HRESIMS as well as 1D and 2D NMR datasets. Antibacterial assay showed that, compounds 1 and 3-5 exhibited strong to moderate antibacterial activities against Micrococcus luteus and Bacillus thuringiensis with MIC values ranging from 0.0625 to 8 µg/mL, while compounds 3 and 6 showed weak antibacterial activities against Staphylococcus aureus and MRSA. The antibacterial activities of the lobophorins in this study indicated that the more substitution number of the sugar moieties at C-9 of the lobophorin, the stronger antimicrobial properties it may deserve, and the higher the oxidation degree of substituent group at C-3D, the better antibacterial activities of its corresponding compound could be.

Modification, Biological Evaluation and SAR Studies of Novel 1H-Pyrazol Derivatives Containing N,N'-Disubstituted Urea Moiety as Potential Anti-melanoma Agents.

Malignant melanomas are amongst the most aggressive cancers. BRAF Inhibitors have exhibited therapeutic effects against BRAF-mutant melanoma. In continuation of our earlier studies on anti-melanoma agents based on 1H-pyrazole skeleton, two sets of novel compounds that include 1H-pyrazole-4-amines FA1 - FA13 and corresponding urea derivatives FN1 - FN13 have been synthesized and evaluated for their BRAFV600E inhibitory and antiproliferation activities. Compound FN10 displayed the most potent biological activity against BRAFV600E (IC50 = 0.066 µm) and the A375 human melanoma cell line (GI50 = 0.81 µm), which was comparable to the positive control vemurafenib, and more potent than our previously reported 1H-pyrazole-3-amines and their urea derivatives. The results of SAR studies and molecular docking can guide further optimization and may help to improve potency of these pyrazole-based anti-melanoma agents.