Ultrasound-assisted solvent extraction of phenolics, flavonoids, and major triterpenoids from Centella asiatica leaves: A comparative study

Centella asiatica has been known for its significant medicinal properties due to abundance of bioactive constituents like triterpenoids and flavonoids. Nevertheless, an appropriate solvent system and extraction technique is still lacking to ensure optimized extraction of bioactive constituents present in C. asiatica. Recently, scientists are more focused towards application of green sustainable extraction techniques for the valuable components from plant matrix owing to their eco-friendly and safe nature. Among these, ultrasonication (US) is known as a valuable strategy for separation of bioactive components from medicinal plants. Hence, current research was performed to observe the effect of ultrasonication in the presence of five different solvents (Water, Hexane, Methanol, Chloroform, and Ethyl acetate) on total phenolic contents (TPC), total flavonoid contents (TFC), antioxidant properties (DPPH, ABTS, Nitric oxide radical activity, and Superoxide anion assay), and four major triterpenoid contents in C. asiatica leaves. Herein, ultrasound assisted methanolic extract (UAME) possessed maximum amount of TPC (129.54 mg GAE/g), TFC (308.31 mg QE/g), and antioxidant properties (DPPH: 82.21 % & FRAP: 45.98 µmol TE/g) followed by ultrasound-assisted Water extract (UAWE), ultrasound-assisted ethyl acetate extract (UAEAE), ultrasound-assisted n-hexane extract (UAHE), and ultrasound-assisted chloroform extract (UACE), respectively. Moreover, the superoxide radical and nitric oxide assays depicted a similar trend, revealing the highest percent inhibition for UAME (SO: 83.47 % & NO: 66.76 %) however, the lowest inhibition was displayed by UACE (63.22 % & 50.21 %), respectively. Highest content of major terpenoids were found in UAME of C. asiatica leaves as madecassoside (8.21 mg/g) followed by asiaticoside (7.82 mg/g), madecassic acid (4.44 mg/g), and asiatic acid (3.38 mg/g). Ultrasound-assisted extraction technique can be an efficient extraction method for bioactive compounds present in C. asiatica. However, ultrasonication along with methanol as an extraction solvent can surely enhance the extraction of valuable constituents. The results of this study provide an insight into major terpenoids, and antioxidants present in extracts of C. asiatica, implicating its use in ancient medicine systems and future drug development.