Abstract
Phenolics- enriched plant food sources are excellent dietary and therapeutic targets to combat the increasing prevalence of diet and lifestyle-influenced non-communicable chronic diseases (NCDs), such as type 2 diabetes (T2D). Among plant sources, edible flowers rich in health protective phenolic compounds provide novel opportunities as ingredient and nutraceutical sources. Roselle (Hibiscus sabdariffa Linn.) is a popular edible flower and consumed as part of traditional cuisines and processed foods in several countries of Asia and Africa. Red calyces of Roselle are rich in phenolic compounds, which potentially have high antioxidant and anti-hyperglycemic properties. Therefore, there is merit in screening of dried Roselle calyces as sources for functional food ingredients or nutraceuticals to counter chronic oxidative stress and chronic hyperglycemia using in vitro assays. This has led to this study to investigate and compare phenolic compounds associated antioxidant and anti-hyperglycemic functions of different organic solvent-extracted fractions of dried Roselle calyces using rapid in vitro assays-based screening strategy. Total soluble phenolic content, profile of phenolic compounds, free radical scavenging assay-based total antioxidant activity, and anti-hyperglycemic function linked α-amylase and α-glucosidase inhibitory activities of four different organic solvents (chloroform, hexane, ethyl acetate, and initial crude extraction in 100% methanol) extracted fractions of calyces of Roselle were determined using in vitro assays. Studies indicated high phenolic-linked antioxidant and anti-hyperglycemic relevant properties in red Roselle calyces, specifically in ethyl acetate and methanol solvent-based extracted fractions. Major phenolic compounds in extracted fractions of Roselle calyces were chlorogenic acid, caffeic acid, gallic acid, catechin, rutin, benzoic acid, and cinnamic acid. Additionally, moderate α-amylase (30–92%) and very high α-glucosidase (81–98%) inhibitory activities were confirmed in undiluted samples of organic solvent-extracted fractions of Roselle calyces in the in vitro assays. Taken together these in vitro screening results indicated that calyces of Roselle are excellent sources of health protective phenolic compounds with high antioxidant and anti-hyperglycemic functions and organic solvent (ethyl acetate and methanol) extracted fractions of this edible flower can be strategically utilized to design functional food ingredients and nutraceuticals.
Highlights
Improving the access and availability of nutritious, human health relevant, safe, and inexpensive plant-based food sources is essential to counter the rapid rise in the prevalence of poor diet and lifestyle-influenced non-communicable chronic diseases (NCDs) worldwide
The phenolic profile results of this study indicated that different phenolic compounds of Roselle calyces have organic solvent specific affinity and solubility based on their polarity and binding property in tissues of Roselle calyces
The antioxidant activity of methanol extracted fraction (97% inhibition) of Roselle calyces based on ABTS+ free radical scavenging assay was statistically at par with ethyl acetate fraction, while it was significantly higher when compared with hexane and chloroform fractions
Summary
Improving the access and availability of nutritious, human health relevant, safe, and inexpensive plant-based food sources is essential to counter the rapid rise in the prevalence of poor diet (higher daily intake of hyper-processed and calorie dense food) and lifestyle-influenced non-communicable chronic diseases (NCDs) worldwide. To find solutions to these NCDlinked challenges, it is essential to diversify contemporary dietary sources by targeting and integrating underutilized plant-based edible sources for wider human health protective functional benefits. Edible flowers offer opportunities with balanced nutrition and rich health protective bioactive profile which are safe dietary sources with therapeutic potential that can be targeted as functional food ingredients or nutraceuticals to prevent and mitigate NCD-related health risks. There is an urgent need to improve nutritional needs with higher daily intake of more diverse and bioactive compounds enriched plant-based foods to address the emerging T2D epidemic-related public health challenges
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