In vitro Antioxidant and Antimicrobial Effects of Ceratostigma plumbaginoides

Abstract

Bioactive compounds, including phenols, flavonoids, and tannins, were quantified in leaves, stems and roots of methanol, n-butanol, diethyl ether and n-hexane extracts of Ceratostigma plumbaginoides Bunge. (Plumbaginaceae) ornamental plants. The antioxidant capacity was measured by the DPPH and linoleic acid assays. The total bioactive compounds, as well as the antioxidant capacities, were the highest in the leaves compared with stems and roots. The methanolic, n-butanol, diethyl ether and n-hexane leaf extracts varied in their antibacterial and antifungal activities. In general, the most sensitive bacterium to leaf extracts was Bacillus cereus and the most resistant was Staphyllococcus aureus, while the most sensitive fungus was Aspergillus flavus and the most resistant one was Penicillium ochrochloron. As the methanolic leaf extract was the most active, it was subjected to column chromatography and two compounds were isolated and identified as 1 (5-hydroxy-2-methyl-1,4-naphthoquinone / plumbagin) and 2 (3,3′-biplumbagin). Compounds 1 and 2 showed the highest antibacterial and antifungal activities compared with other extracts tested. The MIC and MBC values for the most active compound 1 were in the range of 0.001 – 0.09 and 0.004 – 0.21 mg mL⁻¹, while MIC and MFC were determined as 0.001 – 0.11 and 0.002 – 0.19 mg mL⁻¹, respectively. The isolated compounds and leaf extracts showed also equal or higher antimicrobial activities compared with antibiotics/commercial reagents which indicate that the plant might be useful for drug development. This is the first report on the antibacterial and antifungal activities, as well as the antioxidant properties of the tested plant parts and isolated compounds.