Phytochemical characterization and antioxidant assessment of Spilanthes acmella leaf extract

People have used medicinal plants in traditional medicine for a very long time, and their phytochemical composition and biological activities remain of scientific interest. This study investigates the phytochemicals, the total phenolic content (TPC), the total flavonoid content (TFC) and the antioxidant activity of extracts from Spilanthes acmella leaves. Methanol, chloroform and hexane were used as solvents, and the extracts were prepared by Soxhlet and ultrasonic-assisted extraction, separately. Simple qualitative tests were performed first to determine the broad classes of phytochemicals. TPC and TFC were then measured by a spectrophotometric method, while the antioxidant activity was determined from the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) scavenging assays. Amongst all the extracts tested, the one made by Soxhlet extraction with methanol had the highest TPC (82.09 ± 1.25 mg GAE/g) and TFC (103.59 ± 1.61 mg QE/g). This same extract was also the best at scavenging radicals, with an IC₅₀ of 147.52 ± 1.07 µg/mL for DPPH and 245.06 ± 1.14 µg/mL for NO scavenging. The differences between the extracts made with the various solvents and extraction methods were statistically significant. The results show that S. acmella leaf extract contains substantial amounts of phenolics and flavonoids and shows marked antioxidant activity, especially when methanol is used as the extraction solvent. The study shows how much the choice of solvent polarity and extraction method affects the extraction of phytochemicals and the antioxidant activity. Clinical trial number: Not applicable.