In Vitro Biological Activities of Alkaloids from Cryptolepis sanguinolenta

Abstract

In our biological screening of higher plants, an aqueous and an 80% EtOH extract from the root bark of Cryptolepis sanguinolenta showed potent antibacterial, anticomplementary, and moderate antiviral activities, but no antifungal effect could be detected. Bioassay-guided fractionation of the 80% EtOH extract led to the isolation of three alkaloids: quindoline (1), hydroxycryptolepine (2), cryptolepine · HCl (3), and the corresponding base cryptolepine (4). All compounds strongly inhibited the growth of Gram-positive bacteria (MIC ≤ 100 µg/ml) and showed a moderate (MIC = 125 or 250 µg/ml), a weak (MIC = 500 µg/ml), or no activity (MIC > 500 µg/ml) against selected Gram-negative bacteria. They also possessed a bactericidal effect depending on the bacterial strain. Compounds 1, 2, and 3 displayed a dose-dependent inhibitory effect on the classical pathway of the complement system while compounds 2 and 3 activated the alternative pathway, except for compound 1. Compound 3 was found to possess an antiherpetic activity. Compounds 1 and 4 showed no antiviral effect, but were quite cytotoxic in the antiviral test system down to a concentration of 1 µg/ml.

Key words

Cryptolepis sanguinolenta - Periplocaceae - antibacterial - anticomplementary and antiviral activities - alkaloids