Comparative Study of Polyphenol Profile after Stimulated Post-intestinal Digestion of Raw and Dried Ginger Leaves

The present study aimed to determine bioaccessibility (BA) of polyphenols (PPs) and flavonoids (FLs) compounds of Ginger (Zingiber officinale) leaves extract after simulated gastrointestinal digestion (GID). One hundred grams of Z. officinale leaves (raw and dried) was extracted with 200 mL of distilled water. Determination of PPs and BA index were carried on the extract before digestion (BD) (undigested), post-intestinal digestion without enzymes (PI-DWOEs) and post-intestinal digestion with enzymes (PI-DWEs) using standard methods. The results showed significant decrease in proanthocyanidins (PCs) and anthocyanins (ACs) of dried and raw Z. officinale in PI-DWEs when compared to PCs and ACs level in BD. A total of nine major PPs compounds were detected in raw Z. officinale leaves in BD and PI-DWOEs, whereas eight PPs were detected in PI-DWEs. In PI-DWOEs, sinapinic acid (6.68 ng/mL) was the most prominent whereas p-coumaric (7.74 ng/mL) was the most protuberant in PI-DWEs. The concentration of total PPs were as follows; BD (41.39 ng/mL) > PI-DWEs (13.6 ng/mL) > PI-DWOEs (19.20 ng/mL). In conclusion, after the in vitro GID of the extract, a good BA index was observed, of which some PPs and FLs contents were near to 100%. However, the reason most PPs and FLs in the extract cannot be available or absorbed intact after digestion could be due to the fact that they undergo a series of reactions with intestinal enzymes. Additionally, not all polyphenols are absorbed equally well. Before it is feasible to predict how PPs will be assimilated by cells, they must first be bioaccessible.