Organ-Specific Chemical Diversity and Biological Activities of Methanolic Extracts from Gaertnera phanerophlebia Baker (RUBIACEAE)

This study focused on the comparison of the chemical and biological profiles of the methanolic extracts from the stems, leaves, and leafy twigs of G. phanerophlebia Baker. This approche is fundamental for the valorization of natural resources. The extraction yields revealed more extractable compounds than the other parts, with the highest yield of 15.37 % found in the leaves, followed by the leafy twigs (11.62 %) and the stems (5.25 %). Despite their lower yield, the leafy twigs exhibited the most significant biological activities. The crude extract from the leafy twigs (ST 380 BTRF) manifested high antiplasmodial activity against Plasmodium falciparum with an IC₅₀ of 16.63 µg/ml compared to the stem and leaf extracts. This extract also demonstrated remarkable antibacterial activity, particularly against Gram-positive bacteria such as Streptococcus pyogenes, Streptococcus pneumoniae, and Staphylococcus aureus, as well as the best antimicrobial effects with bactericidal activity against certain strains. However, no antifungal activity was observed against Candida albicans in any part of the plant. The evaluation of antioxidant activity using the DPPH assay revealed strong free radical scavenging capacity for all plant part extracts, especially the leafy twigs, whose IC₅₀ (12.56 µg/ml) was close to that of α-tocopherol. These results suggest that G. phanerophlebia Baker, particularly the leafy twigs, is a promising source of bioactive compounds with pharmacological potential. Additionally, this study also confirmed that secondary metabolites are not uniformly distributed, and each plant organ possesses its own chemical profile and specific biological activities.