A factorial design to optimise the extraction of phytochemicals from Carpobrotus edulis

Background: Carpobrotus edulis is widely used in traditional medicine to treat several health problems in South Africa. Phytochemical screening of medicinal plants involves several assays and requires a reasonable amount of starting material. Several factors, including plant species and variety, growth conditions, plant age and harvesting time, and plant part, can influence the extraction yield and quality of medicinal plant extracts. Aim: This research aimed to optimise extraction yields from C. edulis using an analytical 23 full factorial design. Setting: The plant material for this study was collected from the dunes along the Bloubergstrand coast (latitude: −33°47’49.92” S and longitude: 18°27’43.20” E) in the Western Cape Province, South Africa. Methods: The factorial design involved two extractants (aqueous and methanolic), two pH levels (7 and 9) and two extraction temperatures (25°C and 40°C) and two extraction periods of 72 and 168 h. Regression models and factorial analysis provided a robust framework for evaluating these variables, including interaction terms that allowed for a better understanding of how combined conditions affect yields differently from individual conditions. Results: The most effective conditions were a pH of 9 and a temperature of 40°C, with extraction times of 72 h for the aqueous extracts and 168 h for the methanolic extracts. Conclusion: A factorial design can systematically optimise the exact extraction parameters to produce the highest yield of bioactive compounds from plants. Contribution: Obtaining the best yield in medicinal plant research can serve several purposes, including conservation of the plant and the need to drive innovation in herbal medicine research.