Phytochemical analysis and biological activities of various parts of <i>Bulbine natalensis</i> (Baker): A comparative study

Abstract

Introduction: Bulbine natalensis is a succulent plant native to South Africa, used to treat various skin conditions. The purpose of this investigation was to analyse the phytochemical content, as well as antioxidant and antibacterial activities of various parts of B. natalensis. Methods: Phytochemical screening tests were performed to investigate the presence of ten compounds from B. natalensis methanol extract. Total phenolic, flavonoid, tannin, and proanthocyanidin content assays were followed to determine their concentrations in B. natalensis. The 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide (H2 O2 ), and iron chelating assays were used to assess the antioxidant activity. To determine the antibacterial properties of B. natalensis against Staphylococcus aureus and Escherichia coli, the agar-well diffusion method was adopted. Results: The phytochemical screening revealed more compounds present in the leaves. The underground stems yielded higher concentrations of total phenolics (1909.2 ± 4.8 mg gallic acid equivalent [GAE]/g), total flavonoids (259.7 ± 27.2 mg quercetin equivalent [QE]/g), and total proanthocyanidins (858.3 ± 1.7 mg catechin equivalent [CE]/g) in comparison to the leaves and roots. The roots showed stronger DPPH (0.36 ± 0.02 mg/mL) and H2 O2 (0.24 ± 0.04 mg/mL) scavenging activities. Only the underground stems and roots showed inhibition against S. aureus with the values of 15.33 ± 0.67 mm and 15.67 ± 0.33 mm, respectively, whereas the leaves displayed the highest inhibition against E. coli (18.33 ± 0.88 mm). Conclusion: The methanolic extracts of B. natalensis leaves, underground stems, and roots possess significant phytochemical content, in conjunction with antioxidant and antibacterial activities.