Phytoconstituent optimization by response surface methodology and pharmaceutical activities of Pelargonium graveolens LʼHér acetone extract

Abstract

Context: Pelargonium graveolens Lʼ Hér is an evergreen shrub, cultivated principally for the medicinal essence and decoction in Southern Africa for the treatment of menopausal problems, tonsillitis, poor circulation, ringworm, and cervical cancer. Objective: We aimed to optimize the extraction of phenolics and flavonoids from P. graveolens by response surface methodology with particular attention on the proliferative and cytotoxic effects on human keratinocytes, as well as the antioxidant and antibacterial activities. Materials and Methods: The optimization was achieved by Box–Behnken design. Extract, metabolite yields, and minimal inhibitory concentrations (MIC) were determined by gravimetric, spectrophotometric, and microdilution methods, respectively. The antiradical potentials were evaluated using the phosphomolybdate, 2,2-diphenyl-1-picrylhydrazyl, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), and lipid peroxidation assays. The kinetics of the lipid protective activity was studied and fitted into models. The proliferative and cytotoxic effects were evaluated using the CellTiter® Blue cell viability and lactate dehydrogenase assay. Results: The regression coefficient r2 ≥ 0.9775 indicated a close correlation between actual and predicted values of the responses. The ideal parameter for the extraction of phenolics and flavonoids by macerations was determined as an extraction time: 9.63–12.01 h, material mass: 2.78–2.62 g, agitation speed: 143.11–191.37 rpm, and solvent volume: 68.06–69.87 mL. Total antioxidant capacity and reducing power were comparable to standard gallic acid, while the antiradical activity has IC50 values of 0.18 ± 0.03–4.98 ± 0.15 mg/mL. Further, the lipid protective revealed a dose-dependent activity fitting into a pseudo-second-order kinetic model. MIC value of 1.56 mg/mL was registered against Staphylococcus aureus and Salmonella typhi compared to chloramphenicol. There was a significant (P < 0.05) increase in cell proliferation and viability when the extract was administered at concentrations of ≤50 μg/mL. However, at ≥100 μg/mL concentration, there was significant cytotoxicity in comparison to the untreated cells. Conclusion: These biological activities are confirmation of the phytomedicinal application and possible source of pharmaceutical compounds. However, administration of the decoction should take into cognizance the antiproliferative effect at doses ≥100 μg/mL as well as the potential to induce and maintain keratinocyte proliferation at low concentration with an eye on the antiproliferative effect at concentrations ≥100 μg/mL.