The study of structure and effects of two new proanthocyanidins from Anogeissus pendula leaves on rumen enzyme activities

Two novel proanthocyanidins, (2R, 3R)-(+)-Gallocatechin-(4β → 8)4-(2R, 3R)-(+)-gallocatechin (compound 1) and 3-O-galloyl-(2S, 3S)-(–)-epicatechin-(4α → 8)-[3-O-galloyl-(2S, 3S)-(–)-epicatechin (4α → 8)]2-(2S, 3S)-(–)-epicatechin (compound 2), were structurally characterized from leaves of Anogeissus pendula. The structures were determined by ultraviolet spectroscopy (UV), proton nuclear magnetic resonance ((1)H NMR), (13)C NMR, and heteronuclear multiple bond correlation. Molinspiration and Osiris property explorer applications were used to predict bioactivity and drug score. Drug scores of 0.08 and 0.05 were predicted for compounds 1 and 2, respectively. Predicted bioactivity scores were high. Due to their molecular weight, chemical structure, and conformation, the newly discovered proanthocyanidins possess an inclination to interact with proteins. Based on this premise, both compounds were subjected to in vitro testing against ruminal enzymes. They exhibited significant inhibition activities (p < 0.01) with a range of half maximal effective concentration (EC(50)) of 14.80–17.88 mg/mL of glutamic oxaloacetic transaminase in both protozoa and bacteria fractions. The ruminal glutamic pyruvic transaminase activity was significantly inhibited (p < 0.01) from EC(50) 12.59–16.29 mg/mL, and R-cellulase inhibition was recorded with EC(50) 18.20–21.98 mg/mL by compounds 1 and 2, respectively. Protease activity decreased with increasing incubation time and concentration of both compounds. The novel proanthocyanidins have potential roles in improving feed conversion ratios and in drug development.