Chuanguang Qin

Solid-phase synthesis and antibiotic activities of cyclodecapeptides on the scaffold of naturally occurring Laterocidin

The development of new antibacterial therapeutic agents capable of halting microbial resistance is a chief pursuit in clinical medicine. Laterocidin and its analogues were synthesized for the first time by solid-phase synthesis method via linking of the carboxyl group on side chain of Aspartate to Rink resin with the protection of side chain alpha-carboxyl group of Aspartate by Dmab as a temporary alpha-COOH protecting group for the on-resin cyclization. Different configuration of N- and C-terminal was benefit to peptide cyclization. Laterocidin analogue 3 (Asp(1)-->Asn(1), Phe(4)-->Tyr(4) and d-Tyr(6)-->d-Phe(6)) demonstrated potent and broad antimicrobial properties, especially exhibited activity against clinical Methicillin-resistant Staphylococcus aureus (L-MRSA) and the gram-negative extended-spectrum beta-lactamases-producing Escherichia coli (ESBLs E. coli) and L-E.coli. This finding has important significance to exploit new antibiotic medicine.

Separation and elucidation of anthocyanins in the fruit of mockstrawberry (Duchesnea indica Focke).

Anthocyanin pigments in the fruit of mockstrawberry (Duchesnea indica Focke), were extracted with 0.1% HCl in ethanol, and the crude anthocyanin extract was purified by a C18 Sep-Pak cartridge open-column chromatography. High-performance liquid chromatography (HPLC) with photodiode array detection and mass spectrometry (MS) was applied for the isolation and composition analysis of anthocyanins in the fruit of mockstrawberry and their aglycones from acid hydrolysis. Three anthocyanins were found in the fruit of mockstrawberry and they were identified as cyanidin 3-O-rutinoside (61%), peonidin 3-O-rutinoside (34%), and petunidin 3-O-rutinoside (5%), respectively, by spectroscopic methods (UV-vis and MS). The two major anthocyanins were isolated by preparative HPLC, and their chemical structures were further characterised by H1 NMR. On the basis of chromatographic data, the total anthocyanin content was 205 mg g−1 of the fresh fruit of mockstrawberry.