Sequential Extraction of Proanthocyanidin Fractions from Ficus Species and Their Effects on Rumen Enzyme Activities In Vitro

Three proanthocyanidin fractions per species were sequentially extracted by 50% (v/v) methanol–water, 70% (v/v) acetone–water, and distilled water from leaves of Ficus racemosa (fractions FR) and F. religiosa (fractions FRL) to yield fractions FR-50, FR-70, FR-DW, FRL-50, FRL-70, and FRL-DW. Fractions were examined for their molecular structure, effect on ruminal enzyme activities, and principal leaf protein (Rubisco) solubilization in vitro. All fractions except FRL-70 contained flavonoids including (+) catechin, (−) epicatechin, (+) gallocatechin, (−) epigallocatechin, and their -4-phloroglucinol adducts. The fractions FRL-50 and FRL-DW significantly (p < 0.05) inhibited the activity of ruminal glutamic oxaloacetic transaminase and glutamic pyruvic transaminase. All fractions inhibited glutamate dehydrogenase activity (p < 0.05) with increasing concentration, while protease activity decreased 15–18% with increasing concentrations. Fractions FRL-50 and FRL-DW completely inhibited the activity of cellulase enzymes. Solubilization of Rubisco was higher in F. religiosa (22.36 ± 1.24%) and F. racemosa (17.26 ± 0.61%) than that of wheat straw (WS) (8.95 ± 0.95%) and berseem hay (BH) (3.04 ± 0.08%). A significant (p < 0.05) increase in protein solubilization was observed when WS and BH were supplemented with FR and FRL leaves at different proportions. The efficiency of microbial protein was significantly (p < 0.05) greater in diets consisting of WS and BH with supplementation of F. racemosa leaves in comparison to those supplemented with F. religiosa leaves. The overall conclusion is that the fractions extracted from F. religiosa showed greater inhibitory effects on rumen enzymes and recorded higher protein solubilization in comparison to the F. racemosa. Thus, PAs from F. religiosa are potential candidates to manipulate rumen enzymes activities for efficient utilization of protein and fiber in ruminants.