Antifungal, acetylcholinesterase inhibition, antioxidant and phytochemical properties of three Barleria species

This study was aimed at evaluating the antifungal, acetylcholinesterase inhibition and antioxidant activities of petroleum ether, dichloromethane, ethanol and methanol extracts from different parts of Barleria prionitis, Barleria greenii and Barleria albostellata. Their phytochemical properties and the possibility of plant-part substitution as a conservation strategy against destructive harvesting (use of aerial parts and roots) of these species for medicinal purposes were also investigated. Microtitre plate assays were used in determining their antifungal (against Candida albicans) and acetylcholinesterase inhibition activities. All the extracts demonstrated both fungistatic and fungicidal activities with the minimum inhibitory concentration ranging from 0.78 to 9.38 mg/ml and minimum fungicidal concentration ranging from 1.17 to 12.50 mg/ml. The higher inhibitory activity of B. greenii leaf extracts in most cases compared to similar extracts of the stems and roots suggest the potential of B. greenii leaves in plant-part substitution. At the lowest extract concentration (0.156 mg/ml), the leaf extract of B. greenii demonstrated a significantly higher acetylcholinesterase (AChE) inhibition than its stem and root extracts. In B. albostellata, the AChE inhibitory activity demonstrated by the stem was significantly greater than that recorded in its leaf extract. These findings suggest that the idea of plant part substitution may be species and/or biological activity dependent. In the DPPH radical scavenging assay, different parts of Barleria species showed free radical scavenging activity with EC50 values ranging from 6.65 to 12.56 μg/ml. The ability of the extracts from different plant parts to reduce ferric ion/ferricyanide complex to the ferrous form and decrease carotenoid bleaching rate suggests the presence of antioxidant compounds capable of donating electrons and hydrogen atoms in their reaction mechanisms. Flavonoids, iridoids and tannins were detected in the different parts of these Barleria species. These phytochemicals might be responsible for the observed biological activities. The isolation of specific bioactive compounds through bioassay-guided fractionation and their characterization as well as studies evaluating their safety may be necessary in the exploration of these species for potential new therapeutic drugs or drug leads.

Research Highlights
► All extracts showed fungistatic and fungicidal activities against Candida albicans.
► The methanolic extracts displayed AChE inhibition and antioxidant properties.
► Higher activities in the leaves indicate a potential for plant-part substitution.
► The observed activities may be due to their iridoid, flavonoid and tannins content.