Antibacterial and antioxidant activity of liquid hand soap with natural colourants derived from butterfly pea (Clitoria ternatea), beetroot (Beta vulgaris) and sappanwood (Caesalpinia sappan) extracts

Handwashing with soap and water is an essential preventive measure to reduce the spread of infections. Extracts from butterfly pea (Clitoria ternatea L.), beetroot (Beta vulgaris L.) and sappanwood (Caesalpinia sappan L.) contain flavonoids, saponins, tannins, steroids and terpenoids that act as antibacterial and antioxidant agents, while also serving as safe natural colourants. This study evaluated their antibacterial and antioxidant activities, both in raw extracts and in liquid hand soap formulations containing 1 % w/v extracts with visually appealing colours. Dried plant materials were extracted through ethanol maceration and formulated into liquid hand soap at 1 % w/v. The parameters evaluated included phytochemical constituents (triterpenoids, alkaloids, tannins and flavonoids), antioxidant activity determined by inhibition percentage and half-maximal inhibitory concentration (IC50), antibacterial activity against Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis) and Gram-negative (Pseudomonas aeruginosa, Escherichia coli) bacteria using the inhibition zone assay. Sappanwood extract showed the highest alkaloid (30.21 mg AE/g) and flavonoid (29.17 mg QE/g) levels, while butterfly pea had the highest triterpenoid (7.62 mg LE/g) and tannin (39.38 mg TAE/g) contents. Sappanwood exhibited the strongest antioxidant activity (88.74 % inhibition, IC50= 0.01 ppm) and potent antibacterial effects, particularly against S. epidermidis (812 mm²). Liquid hand soap with 1 % w/v beetroot extract showed significant antibacterial activity, with inhibition zones of 438 mm² (S. aureus), 425 mm² (P. aeruginosa), 281 mm² (S. epidermidis) and 376 mm² (E. coli). These findings highlight the potential of 1 % w/v plant-derived extracts as multifunctional additives in hygiene products, combining antimicrobial, antioxidant and coloring properties, with promising applications for eco-friendly personal care formulations.