Background: Scaevola spinescens is an endemic Australian shrub that is linked to various health benefits and traditionally used as medicine by decoction. To date, the extraction efficiency of the plant under various conditions has not been well understood. This study aimed to optimize aqueous extraction conditions of S. spinescens, for maximum extraction of total phenolic compounds, flavonoids and saponins, as well as antioxidant activities.
Methods: Response surface methodology was used to determine the influence of four independent parameters including temperature, time, sample-to-water ratio and pH. The optimal ranges of temperature (60-90 °C), time (30-60 min), sample-to-water ratio (2-6 g/100 mL) and pH (3-7) were determined in preliminary experiments. Following assessment and optimization of the response surface methodology models, validation experiments were conducted to compare predicted and experimental values.
Results: The RSM models showed that extraction temperature, time and sample-to-water ratio significantly affected total phenolic compound yields. Extraction temperature and time significantly affected flavonoid yields, while only sample-to-water ratio significantly affected saponin yields. Optimal conditions for extraction were determined to be: 90 ºC, 53 min, 2:100 (g/mL), and pH of 4.5, if saponins are the target compounds for extraction. For phenolics, flavonoids and antioxidant capacity, a higher sample-to-water ratio of 6:100 (g/mL) is recommended.
Conclusion: Response surface methodology proved to be a reliable method for predicting yields of bioactive compounds and antioxidant capacity in S. spinescens. These findings can be used for efficient decoction by practitioners and end users, or by researchers for further isolation and purification of bioactive compounds from S. spinescens extracts.