Polyphenol release during domestic processing and simulated digestion of beans (Phaseolus vulgaris and Vicia faba) and their anti-inflammatory effects in RAW264.7 macrophages.

Phaseolus vulgaris and Vicia faba beans contain polyphenols that are associated with chronic disease prevention; yet, their benefits may be limited by their bioaccessibility. Bean polyphenol bioaccessibility is unknown and information about their biological effects is scarce. Therefore, to assess these parameters, the polyphenols released after and optimized in vitro digestion method were determined and the anti-inflammatory effect of three P. vulgaris Mexican beans (Negro Jamapa, Marcela and Azufrado) was tested in RAW 264.7 macrophages. Enzymatic digestion extracted around twenty times more polyphenols compared to domestic processing and acid hydrolysis. Starch digestion released four times more polyphenols compared to protein digestion. The main polyphenols released during digestion were conjugates of catechin, sinapic acid, and p-coumaric acid. Domestic processing mainly released flavonoids which are likely to come from the bean hull. All the beans presented a slightly variable polyphenolic profile. Sinapic acid and Negro Jamapa bean exhibited an anti-inflammatory effect by reducing inflammatory related target genes (IL6 and TNFα for sinapic acid and IL6, iNOS and IL1β for Negro Jamapa bean). However, Marcela and Azufrado beans showed a pro-inflammatory effect.

Bean polyphenols bioaccessibility appears to be higher than previously reported and appears to be limited by interactions with starch. This is the first time that starch-polyophenol interaction has been observed in beans. More studies are needed to understand the function of this interaction in plants. This study showed that polyphenol composition in beans is variable, which reflects in the different outcomes obtained during the cell culture experiments. Hence, different beans might exert diverse positive or negative health benefits. More studies are required
to know the health properties of different beans in order to know which are more
recommended to consume.