Identification of Antioxidant, Antimicrobial, and Cytotoxic Compounds From Hymenocardia acida Tul. Using...

Hymenocardia acida Tul. is a medicinal plant used in Angola to treat microbial diseases. It is a well-known plant among local populations; however, few studies have focused on the assessment of phytochemicals associated with their biological activities. Hence, there is a need to evaluate the metabolomic profile of compounds that contribute to the antimicrobial, antioxidant activities, and cytotoxic effects of H. acida. This study investigated the chemical profile, antimicrobial and antioxidant activities, and cytotoxic effects of compounds derived from different plant organs of H. acida. The compounds were analyzed using ultra-high-performance liquid chromatography-quadrupole-electrostatic field orbitrap mass spectrometry, and the resulting data were further analyzed using a molecular networking approach. Thirty-two natural compounds were annotated, including flavonoids, fatty acids, coumarins, terpenoids, alkaloids, anthocyanins, saponins, polyphenols, glycosides, and disaccharides. These families of natural compounds were differentially distributed in various plant parts, indicating chemical differences among the leaf, root, and stem bark extracts of H. acida, which were annotated for the first time in this plant. The crude stem bark (IC₅₀ = 3.031 ± 1.610 µg/mL) and root (IC_0.5 = 0.019 ± 0.000 µg/mL) extracts exhibited the highest antioxidant activity, as determined by 2,2-diphenyl-1-picrylhydrazyl radical scavenging and reducing power assays, respectively. In contrast, using microbroth dilution methods, the leaf extracts exhibited activity against all tested microorganisms (Streptococcus agalactiae, Escherichia coli, Staphylococcus aureus, Candida tropicalis, Candida albicans, Staphylococcus subsp. aureus, Staphylococcus epidermidis, Klebsiella pneumonia, and Pseudomonas aeruginosa) compared to the root and stem bark extracts, with minimal inhibitory concentrations ranging from 1 to 0.0078125 mg/mL. Stem bark and root extracts did not inhibit the visible growth of E. coli, S. aureus, C. tropicalis, and C. albicans. The methanol leaf extracts showed significant cytotoxic effects against Vero cells at 250 and 500 µg/mL, whereas the dichloromethane leaf extracts were cytotoxic to Vero cells at 500 µg/mL. The stem bark and root extracts were not cytotoxic at any concentration. Therefore, the annotated natural compounds may contribute to the antimicrobial, antioxidant, and cytotoxic effects of H. acida. These natural compounds offer promising avenues for the discovery and development of new lead drugs for the management and treatment of microbial diseases. Molecular networking provided a detailed phytochemical overview of this plant species. Furthermore, the results reported in this study highlight the importance of investigating bioactive chemical compounds in H. acida and provide new insights into the phytochemical annotation and pharmacological properties of extracts from various parts of H. acida.