Sacred lotus (Nelumbo nucifera) has long been used as a food source and ingredient for traditional herbal remedies. Plant parts contain neuroprotective agents that interact with specific targets to inhibit Alzheimer’s disease (AD). Organic solvents including methanol, ethyl acetate, hexane, and n-butanol, are widely employed for extraction of sacred lotus but impact food safety. Seed embryo, flower stalk, stamen, old leaf, petal, and leaf stalk of sacred lotus were extracted using hot water (aqueous extraction). The extractions were analyzed for their bioactive constituents, antioxidant and anti-AD properties as key enzyme inhibitory activities toward acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase 1 (BACE-1). Results showed that the sacred lotus stamen exhibited significant amounts of phenolics, including phenolic acids and flavonoids, that contributed to high antioxidant activity via both single electron transfer (SET) and hydrogen atom transfer (HAT) mechanisms, with anti-AChE, anti-BChE, and anti-BACE-1 activities. To enhance utilization of other sacred lotus parts, a combination of stamen, old leaf and petal as the three sacred lotus plant components with the highest phenolic contents, antioxidant activities, and enzyme inhibitory properties was analyzed. Antagonist interaction was observed, possibly from flavonoids–flavonoids interaction. Further in-depth elucidation of this issue is required. Findings demonstrated that an aqueous extract of the stamen has potential for application as a functional food to mitigate the onset of Alzheimer’s disease.

Anthocyanidins are bioactive compounds found mostly in colored plants and fruits. Consumption of anthocyanidin-rich foods has been shown to reduce the risk of diabetes. However, limited information is available regarding the inhibitory effect and interactions of anthocyanidins on α-glucosidase, the key enzyme that controls diabetes through degrading carbohydrate. Therefore, we used computational docking analysis to investigate the degree and type of inhibition by α-glucosidase, and the structural interactions of enzyme-selected anthocyanidins. The results suggested that anthocyanidins exhibit half maximal inhibitory concentration of 4∼55 μM; the strongest and weakest α-glucosidase inhibitors were delphinidin and malvidin, respectively. Indeed, delphinidin inhibits α-glucosidase in a mixed type, close to non-competitive manner with an inhibitory constant of 78 nM. Addition of a glycoside (glucoside or galactoside) at C3 on the C ring of delphinidin significantly decreased inhibitory activity, and addition of glycosides at C3 on the C ring and C5 on the A ring of delphinidin prevented all inhibitory activity. Molecular docking and free binding energy accurately confirmed the mode of inhibition determined by enzyme kinetics. These data will inform the use of alternative sources of anthocyanidins in functional foods and dietary supplements for prevention of diabetes. The results provide useful information for evaluating possible molecular models using anthocyanins/anthocyanidins as templates and α-glucosidase as the key enzyme in management of diabetes.

Oxidative stress contributes to defective antioxidant defenses, which may lead to type 2 diabetes (T2D). This study aimed to elucidate the T2D risks and antioxidant defenses by investigating the superoxide dismutase (SOD), catalase (CAT), vitamin A, and vitamin E status. We observed 102 participants aged 35–66 years from Sung Neon, Nakhon Ratchasima, Thailand. The blood samples were collected to measure the SOD, CAT, vitamin A, and vitamin E concentrations. The SOD and CAT activities were inversely associated with T2D risk. When compared with participants in the highest quartile of SOD and CAT, those in the lowest quartile for T2D risk obtained multivariable-adjusted odds ratios of 4.77 (SOD: 95% confident interval CI, 1.01–22.40; p = 0.047) and 4.22 (CAT: 95% CI, 1.07–16.60; p = 0.039). The possible influencing factors (e.g., physical activity, total cholesterol, and triglyceride) might mediate the association of SOD and CAT with T2D risk. Meanwhile, the relationship between vitamin A and vitamin E concentrations and T2D risk was insignificant. In conclusion, lower concentrations of antioxidant enzyme activity (SOD and CAT) may be an additional risk factor for T2D.