Antibacterial activity of the alkaloid-enriched extract from Prosopis juliflora pods and its influence on in vitro ruminal digestion

Abstract

The purpose of this study was to assess the in vitro antimicrobial activity of alkaloid-enriched extracts from Prosopis juliflora (Fabaceae) pods in order to evaluate them as feed additives for ruminants. As only the basic chloroformic extract (BCE), whose main constituents were juliprosopine (juliflorine), prosoflorine and juliprosine, showed Gram-positive antibacterial activity against Micrococcus luteus (MIC = 25 μg/mL), Staphylococcus aureus (MIC = 50 μg/mL) and Streptococcus mutans (MIC = 50 μg/mL), its influence on ruminal digestion was evaluated using a semi-automated in vitro gas production technique, with monensin as the positive control. Results showed that BCE has decreased gas production as efficiently as monensin after 36 h of fermentation, revealing its positive influence on gas production during ruminal digestion. Since P. juliflora is a very affordable plant, this study points out this alkaloid enriched extract from the pods of Prosopis juliflora as a potential feed additive to decrease gas production during ruminal digestion.

Figure 1

Acid-base fractionation of the ethanolic extract directed to isolation of alkaloids. Adapted from [40].

Figure 2

Chemical structures of juliprosopine (1), prosoflorine (2) and juliprosine (3).

Figure 3

HRESIMS and HPLC-MS analyses of BCE. (A) Direct injection of BCE onto HRESIMS apparatus; (B) HPLC-MS chromatogram obtained for BCE. Chromatographic conditions: see experimental section.

Figure 3

HRESIMS and HPLC-MS analyses of BCE. (A) Direct injection of BCE onto HRESIMS apparatus; (B) HPLC-MS chromatogram obtained for BCE. Chromatographic conditions: see experimental section.

Figure 4

Cumulative gas production (mL/g DM) during ruminal fermentation in samples containing increasing concentrations of BCE (i.e., 0, 25, 50, 100 and 200 mg/L) or monensin (Mon, 5 μM), adjusted by the dual-pool model [41].