Antioxidant Activity, Polyphenolic Content, and FT-NIR Analysis of Different Aspilia africana Medicinal Plant Tissues

Aspilia africana has been used for generations to treat many diseases in Africa. Its biological activities, including antioxidant and anti-inflammatory potential, are attributed to a number of secondary metabolites, including alkaloids and polyphenolics. The antioxidant activities of A. africana callus (CA), juvenile in vitro leaf (IL) and root (IR), ex vitro root (SR) and leaf (SL), and wild leaf (WL) dried samples were assessed based on their diphenylpicrylhydrazyl (DPPH) free radical scavenging abilities. The total phenolic and flavonoid content of different plant samples was compared. Further, high-pressure liquid chromatography (HPLC) was used to quantitatively determine chlorogenic acid content in the A. africana plant samples. Fourier transform near-infrared (FT-NIR) analysis was also carried out to compare the antioxidant phytochemical content in the A. africana plant tissues. Among the samples, IR, with the highest total phenolic content (167.84 ± 1.057 mg GAE/g), total flavonoid content (135.06 ± 0.786 mg RUE/g), and chlorogenic acid (5.23 ± 0.298 mg/g) content, had the most potent antioxidant activity (IC₅₀ = 27.25 ± 5.028 μg/mL), followed by WL. The lowest polyphenolic content and antioxidant activity were observed in SR. The antioxidant activities of A. africana tissues were positively correlated with the total phenolic and flavonoid content in the samples. The differences in antioxidant activities of A. africana tissues could be attributed to the difference in their polyphenolic content. Our study reports, for the first time, the antioxidant activities of A. africana callus and roots (in vitro and ex vitro). The A. africana samples IR, CA, and WL could be valuable natural sources of antioxidants that could be further exploited for the development of useful pharmaceutical products.