Antimicrobial and antiquorum-sensing activity of extracts and ricinine derivatives.

Ricinine (), a known major alkaloid in plant, was used as a starting compound for the synthesis of six ricinine derivatives; two new and four known compounds. The new derivatives; 3-amino-5-methyl-1-pyrazolo[4,3-c]pyridin-4(5)-one (), and 3-amino-5-methyl-1-(phenylsulfonyl)-1-pyrazolo[4,3-c]pyridin-4(5)-one (), as well as the previously prepared derivatives (-) were subjected for antimicrobial and antiquorum-sensing evaluation in comparison to different extracts. Acetyl ricininic acid derivative ( showed the highest antimicrobial activity among all tested derivatives against , , , and . However, compound (4-methoxy-1-methyl-2-oxo-1,2-dihydropyridine-3-carboxamide) showed the highest antiquorum-sensing activity among all tested compounds and extracts. These findings proved the usefulness of ricinine as a good scaffold for the synthesis of new antimicrobial and antiquorum-sensing derivatives in spite of its poor contribution to the antimicrobial activity of the plant extracts.