Antimicrobial, Antigenotoxicity, and Characterization of Calotropis procera and Its Rhizosphere-Inhabiting Actinobacteria: In Vitro and In Vivo Studies

Abstract

<i>Calotropis procera</i> (<i>C. procera</i>) is a wild shrub that is a medicinal plant found in abundance throughout Saudi Arabia. In this study, we investigated the phytochemical composition and antigenotoxic properties of the ethanolic extract of <i>C. procera</i>, in addition to the antimicrobial activity of the plant and its rhizospheric actinobacteria effects against pathogenic microorganisms. Soil-extract medium supplemented with glycerol as a carbon source and starch-casein agar medium was used for isolation of actinobacteria from rhizosphere. From the plant, a total of 31 compounds were identified using gas chromatography/mass spectrometry (GC-MS). The main components were α-amyrin (39.36%), lupeol acetate (17.94%), phytol (13.32%), hexadecanoic acid (5.55%), stigmasterol (3.16%), linolenic acid (3.04%), and gombasterol A (2.14%). <i>C. procera</i> plant extract's antimicrobial activity was investigated using an agar well-diffusion assay and minimum inhibitory concentration (MIC) against six pathogenic microbial strains. The plant extract of <i>C. procera</i> was considered significantly active against <i>Staphylococcus aureus</i>, <i>Klebsiella pneumonia</i>, and <i>Escherichia coli</i>, with inhibition zones of 18.66 mm, 21.26 mm, and 21.93 mm, respectively. The plant extract was considered to be a moderate inhibitor against <i>Bacillus subtilis</i>, with MIC ranging from 0.60-1.50 mg/mL. On the other hand, the isolated actinobacteria were considered to be a moderate inhibitor against <i>S. aureus</i> (MIC of 86 µg/mL), and a potent inhibitor, strain CALT_2, against <i>Candida albicans</i> (MIC of 35 µg/mL). The 16S rRNA gene sequence analysis showed that the potential strains belonged to the genus <i>Streptomyces.</i> The effect of <i>C. procera</i> extract against cyclophosphamide (CP)-induced genotoxicity was examined by evaluating chromosome abnormalities in mouse somatic cells and DNA fragmentation assays. The current study revealed that oral pretreatment of <i>C. procera</i> (50, 100, and 200 mg/kg b.w.) for 1, 7, and 14 days to cyclophosphamide-treated animals significantly reduced chromosomal abnormalities as well as DNA fragmentation in a dose-dependent manner. Moreover, <i>C. procera</i> extract had antimicrobial and antigenotoxic effects against CP-induced genotoxicity.