In Vitro Antibacterial, DPPH Radical Scavenging Activities, and In Silico Molecular Modeling of Isolated Compounds from the Roots of Clematis hirsuta.

Abstract

Clematis hirsuta is one of the traditional medicinal plants used in Ethiopia to treat different ailments, such as cancer and diseases related to the respiratory system. This study aimed to isolate the phytochemical components of the root of C. hirsuta and evaluate their in vitro and in silico biological activities. Oleic acid (1), palmitic acid (2), sterols (3 and 4), boehmenan (5), and carolignans E (6 and 7) were isolated by silica gel column chromatography and preparative thin layer chromatography and characterized by NMR spectroscopy. Compounds 5-7 were isolated from the plant for the first time. At 5 mg/mL, the inhibition zone of evaluated compounds ranged from 8.80 to 11.10 mm against all selected bacteria. The MIC of the MeOH and n-hexane: EtOAc (1 : 1) extracts was greater than or equal to 50 mg/mL against all selected bacteria. At 62.5 μg/mL, the % DPPH radical scavenging activity of tested compounds ranged from 30.3% to 92.1% with an IC₅₀ value of 19.4 to 2.1 μg/mL. The results of molecular docking studies indicated that the docking scores of compounds 3-7 ranged from -6.4 to -7.9 kcal/mol against E. coli DNA gyrase B, -8.3 to -9.0 kcal/mol against the Pseudomonas quinolone signal A, -7.1 to -8.5 kcal/mol against pyruvate kinase M2, and -7.9 to -8.5 kcal/mol against human topoisomerase IIβ. The results of the in silico antibacterial activity of compounds 3, 5, and 6 supported the in vitro antibacterial test results. Compound 5 had a better docking score against human topoisomerase IIβ than the other test samples demonstrating its potential as an anticancer agent. Therefore, compounds 3-7 could be considered as a lead for developing antibacterial and anticancer drugs. Moreover, the presence of these active phytochemicals supports the traditional use of this plant against cancer and bacteria.