Phytochemical investigation of Aloe pulcherrima roots and evaluation for its antibacterial and antiplasmodial activities

Medicinal plants with documented traditional uses remain an important source for the treatment of a wide range of ailments. Evidence shows that majority of the Ethiopian population are still dependent on traditional medicine. Aloe pulcherrima Gilbert & Sebsebe is one of the endemic Aloe species traditionally used for the treatment of malaria and wound healing in central, Southern and Northern part of Ethiopia. The aim of the current study was, therefore, to isolate active compounds from roots of A. pulcherrima and evaluate for their antibacterial and antiplasmodial activities using standard test strains. Bioassay-guided sequential extraction and column chrom-atographic separation were employed for the isolation of bioactive pure compounds. The structures of the compounds were determined by 1D and 2D NMR spectro-scopic techniques. Disk diffusion method was employed to evaluate the antibacterial activities of the isolated compounds against four bacterial strains specifically (Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Escherichia coli ATCC 35218, Pseudomonas aeruginosa ATCC 27853). The malaria SYBR Green I-based in vitro assay technique was used for in vitro antiplasmodial activity evaluation of the compounds against chloroquine resistant (D6) and -sensitive (W2) strains of P. falciparum. Three compounds, chrysophanol, aloesaponarin I and aloesaponarin II were isolated from the acetone extracts of roots of A. pulcherrima. Evaluation of antibacterial activities revealed that aloesaponarin I and aloesaponarin II had significant activities against all the bacterial strains with inhibition zone diameters ranging from 18-27 mm as compared to the reference drug (gentamicin), which displayed inhibition zone diameter ranging between 20 mm (B. subtilis) and 25 mm (P. aeruginosa). The isolated compounds showed moderate in vitro antiplasmodial activity against both chloroquine resistant (W2) -sensitive (D6) strains. Isolation of chrysophanol, aloesaponarin I and aloesaponarin II from roots of A. pulcherrima is the first report of its kind. The finding could be used for further comprehensive evaluation of the isolated compounds for their antibacterial and antimalarial activities besides consideration of the same for potent drug development.