Title : Phytochemical composition, antioxidant capacity, heavy metal safety, and antimicrobial efficacy of lannea welwitschii and lannea velutina extracts from Ghana

Background: Lannea velutina and Lannea welwitschii are widely employed in Ghanaian traditional medicine for managing chronic wounds, diabetes, and infectious ailments. Despite their ethnomedicinal prominence, comprehensive scientific data regarding their phytochemical composition, antioxidant capacity, heavy metal contamination safety, and antibacterial efficacy remain limited.

Methods: Methanol and hydroethanol root and stem bark extracts from both species were evaluated. Quantitative assays determined total phenolic content (TPC), total flavonoid content (TFC), and total tannin content (TTC). Antioxidant potential was assessed using 2,2-diphenyl-1picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and total antioxidant capacity (TAC) assays. Toxic metallic contamination (Fe, Zn, Ni, Cu, Pb) was analyzed alongside Fourier-transform infrared (FTIR) spectroscopic profiling. Antimicrobial activity against Escherichia coli, Staphylococcus saprophyticus, and Proteus mirabilis was determined via microbroth dilution (MIC and MBC).

Results: The extracts exhibited high concentrations of secondary metabolites, with the methanolic stem bark extract yielding the highest TFC (52.45 ± 5.05 mg/g QE), TPC (260.22 ± 1.45 mg/g GAE), and TTC (21.97 ± 0.53 mg/g). Strong antioxidant activity was demonstrated across assays, highlighted by a DPPH EC₅₀ of 0.63 ± 0.01 mg/mL, a FRAP value of 2.37 ± 0.06, and a TAC of 860.34 ± 1.22 mg/g GAE. Heavy metal levels across all extracts were below detectable limits, confirming an acceptable toxicological safety profile. Antimicrobial testing revealed MIC values ranging from 1.5625 to 50 mg/mL and MBC values from 3.125 to 100 mg/mL. Methanolic stem bark displayed the highest antibacterial potency (MIC = 1.5625 mg/mL across all pathogens). Crucially, all MBC/MIC ratios were ≤ 4, establishing definitive bactericidal activity against both Gram-positive and Gram-negative pathogens.

Conclusion: Lannea velutina and Lannea welwitschii possess robust antioxidant capabilities, high bioactive polyphenol yields, bactericidal potency, and freedom from hazardous heavy metal contamination. These findings provide baseline scientific validation for their ethnomedicinal use in wound care and establish a strong foundation for future preclinical drug discovery and phytomedicine standardization.

Sylvester Yeboah is a Ghanaian biomedical researcher with a BSc in Biochemistry and Biotechnology from Kwame Nkrumah University of Science and Technology (KNUST). He serves as a Research Assistant at the Kumasi Centre for Collaborative Research in Tropical Medicine (KCCR) and is the Founder and CEO of the Care Connect GH Foundation. His research focuses on natural product drug discovery, phytochemical profiling, infectious disease epidemiology, and vector biology. He is actively involved in evaluating bioactive compounds, antimicrobial resistance, and translational health initiatives across Ghana.