Physicochemical Assessment and Evaluation of Antibacterial and Antioxidant Activity of Madecassoside Gels

Madecassoside is one of the triterpenoids saponin from the extract of Centella asiatica, which possesses excellent antimicrobial and antioxidant properties. The topical madecassoside gel could be an alternative for the management of local skin problems such as wounds, scars, eczema and psoriasis. In this study, madecassoside gels (F1-F7) were prepared using two different types of polymers with different concentrations: 0.5, 1 and 2% w/w Carbopol-940 and 2, 2.5, 3 and 8% w/w hydroxypropyl methylcellulose (HPMC). The physiochemical properties (physical appearance, pH, grittiness, spreadability and rheological study) of F1-F7 were evaluated. The antimicrobial activity of the gels was determined using the streak plate method and the radical scavenging activity (RSA) was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. F1 was the optimal formulation for Carbopol-940 gel as it exhibited the best spreadability (4.67 ± 0.28 cm) compared to F2 (3.47 ± 0.05 cm) and F3 (3.07 ± 0.05 cm). Meanwhile, F7 was the only optimal formulation for the HPMC gel as it exhibited viscoelasticity behaviour. The antimicrobial activity of F7 against Escherichia coli (E. Coli) and Staphylococcus aureus (S. Aureus) was comparable to 1% madecassoside solution alone and was ~1.2-folds higher than F1 in both bacteria (p < 0.05). The %RSA decreased in the manner of F7 > 1% madecassoside solution > F1. Interestingly, the %RSA of F7 with 1% madecassoside (52.98 ± 0.15%) and F7 without 1% madecassoside (53.28 ± 0.61%) were comparable. In conclusion, HPMC is an antioxidant and acts as an effective protective coating for the active drug.