Schottiin, a new prenylated isoflavones from Psorothamnus schottii and antibacterial synergism studies between methicillin and fremontone against methicillin-resistant Staphylococcus aureus ATCC 1708

• Published in: Natural product research Vol. 36; no. 12; pp. 2984 - 2992
• Main Authors: Kumarihamy, Mallika, Tripathi, Siddharth K., Khan, Shabana, Muhammad, Ilias
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 15.06.2022; Taylor & Francis Ltd
• Subjects: additive effect; Antibacterial activity; antibacterial properties; Antimicrobial; antiplasmodial; antiplasmodial properties; Antiprotozoal agents; Biocompatibility; Biological activity; Chloroquine; Cytotoxicity; Drug resistance; Ethanol; Isoflavones; mammals; Methicillin; methicillin-resistant Staphylococcus aureus; Minimum inhibitory concentration; MRSA; NMR; Nuclear magnetic resonance; Plasmodium falciparum; prenylated isoflavones; Psorothamnus; Psorothamnus schottii; schottiin; spectral analysis; Staphylococcus aureus; Synergism; synergistic activity; Toxicity; Vancomycin; Vero cells
• ISSN: 1478-6419; 1478-6427; 1478-6427
• DOI: 10.1080/14786419.2021.1937157

Bioactivity guided isolation of an ethanol extract of the root of Psoromanthus schottii (Family Fabaceae) afforded a new prenylated isoflavone, named schottiin (5,7,5'-trihydroxy-4'-O-methyl-6'-(3,3-dimethylallyl)-isoflavone) (1), together with four other isoflavones, including fremontone (2), 5,7,4',5'-tetrahydroxy-2'-(3,3-dimethylallyl)-isoflavone (3), glycyrrhisoflavone (4) and fremontin (5), of which 3 and 4 identified as isomeric mixture. Structures of 1-5 were determined by full spectroscopic analyses. A comprehensive 2 D NMR spectral data has allowed revising the structure of fremontone as 2 from previously reported 2 A. Compound 2 showed weak in-vitro antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). A combination study using a checkerboard assay between fremontone (2) and methicillin exhibited a synergistic activity with 8-fold decrease in MIC of methicillin, as well as an additive effect with vancomycin against MRSA ATCC 1708. Compounds 1 and 2 also showed moderate antiplasmodial activity against chloroquine-sensitive (D6) and -resistant (W2) strains of Plasmodium falciparum with no cytotoxicity to mammalian Vero cells.