Evaluation of Antimicrobial Activity of Guava (Psidium guajava) and Utazi (Gongronema latifolium) Leaf Extracts against Oral Microorganisms

Abstract

Oral infections caused by pathogenic microorganisms remain a major public health concern due to increasing antimicrobial resistance and the side effects associated with synthetic antibiotics. This study evaluated the antimicrobial activity of Psidium guajava (guava) and Gongronema latifolium (Utazi) leaf extracts against selected oral microorganisms. Fresh leaves of both plants were collected, air-dried, powdered, and extracted using ethanol and aqueous solvents. Standard microbiological techniques, including agar well diffusion, Minimum Inhibitory Concentration (MIC), and Minimum Bactericidal Concentration (MBC) methods, were used to assess antimicrobial activity against Streptococcus mutans, Staphylococcus aureus, Candida albicans, and Lactobacillus species. Phytochemical screening was also carried out to identify the bioactive constituents present in the extracts. The results showed that both plant extracts possessed significant antimicrobial activity against the tested oral pathogens in a concentration-dependent manner. Psidium guajava demonstrated the highest inhibitory activity against Streptococcus mutans with a zone of inhibition of 22.4 ± 0.5 mm at 100 mg/mL, while Gongronema latifolium recorded 20.8 ± 0.4 mm against the same organism. Lower MIC and MBC values were observed in Psidium guajava, indicating stronger antimicrobial potency. Phytochemical analysis revealed the presence of alkaloids, flavonoids, tannins, saponins, glycosides, terpenoids, and phenolic compounds in both extracts. The study concluded that Psidium guajava and Gongronema latifolium possess significant antimicrobial properties and could serve as potential natural alternatives for the management of oral infections and development of herbal oral healthcare products.