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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.

Rehmannia glutinosa is an important medicinal crop that has been widely used globally to treat various ailments such as hematinic deficiencies, diabetes, and adrenal disorders. To provide a sustainable supply to meet large demands, alternative cultivation methods, apart from conventional ones, are indispensable. This study developed an optimized condition for R. glutinosa adventitious root culture and a scale-up production system using a bioreactor. A woody plant medium enriched with vitamins, 30 g/L sucrose, and 2.0 mg/L 1-naphthaleneacetic acid (NAA) supported the optimum growth rate of adventitious roots (growth index of 25.67). The application of methyl jasmonate (MeJa) at a concentration of 200 μM showed the best enhancement of acteoside biosynthesis, with an approximately 2.53-fold increase (14.37 mg/g dry weight [DW]) compared with the control (5.67 mg/g DW). However, all treatments with MeJa and salicylic acid reduced the biomass of R. glutinosa adventitious roots compared with control. To validate the optimized protocol, the culture system was scaled up by comparing shake flask cultures with 2- and 20-L balloon type (air lift) bubble bioreactors (BTBB) along with elicitation using 200 μM MeJa. The 20-L BTBB cultures produced good-quality R. glutinosa roots with higher biomass (15.94 g DW), acteoside content (22.13 mg/g DW), and antioxidant activity (84.22 %) than shake flask cultures. In addition, fourier transform near-IR (FT-NIR) analysis showed no significant difference in the chemical composition of the in vitro adventitious roots and those that were commercially available. Thus, these findings will provide a basis for the development of large-scale R. glutinosa adventitious root production to meet the demands of pharmaceutical and oriental medicine industries without affecting its availability in nature.