Evaluation of anti-ageing potential of lemongrass tea and its mechanisms of action

Ageing is a complex process that involves the loss of physiological integrity and negatively impacts the well-being of an organism. It is associated with various diseases such as hypertension, cardiovascular and neurodegenerative diseases. However, the proportion of geriatrics is increasing globally, and they are susceptible to these diseases. Regrettably, there is no known medication for managing ageing and its associated complications. One of the plants that is widely consumed as tea is lemongrass (Cymbopogon citratus) due to its aroma and refreshing taste. Several studies have reported the pharmacological properties of lemongrass, but there is no information on its effect on ageing. Therefore, this study investigated the anti-ageing properties of Cymbopogon citratus (lemongrass) tea using in vitro, in silico and in vivo techniques. Fresh and dry lemongrass infusions were subjected to proximate, mineral, amino acid, and phytochemical analysis using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), high-performance liquid chromatography (HPLC), and Liquid Chromatography – Mass Spectrometer (LC-MS). This was followed by the determination of the antioxidant, anti-ageing and neuroprotective potentials of the lemongrass infusion using in vitro methods. Computational techniques, including molecular docking, molecular dynamics simulation and pharmacokinetic profiling, were employed to probe the possible mechanism of anti-ageing effects of the lemongrass teas. The in vivo anti-ageing property of the lemongrass teas was evaluated by including different concentrations of the teas in the diet of D-galactose-induced ageing in Drosophila melanogaster for 14 days, followed by determination of both biochemical and molecular parameters. The results showed that both fresh and dry lemongrass teas are rich in nutrients and phytochemicals. While both lemongrass infusions have similar neuroprotective effects in vitro, the dry lemongrass infusion exhibited better antioxidant activities (with lower EC50 values for DPPH, hydroxyl and superoxide radicals), and these are comparable to the reference standard, gallic acid. It also displayed better anti-ageing properties (with lower IC50 values for inhibition of collagenase, elastase, hyaluronidase and tyrosinase) similar to the standard, oleanolic acid. In the in-silico studies, kaempferitrin had the lowest binding energy for collagenase (-41.57 kcal/mol) and hyaluronidase (-52.09 kcal/mol), while lonicerin and isovitexin-2”-O-arabinoside possessed the lowest binding energies for elastase (-35.55 kcal/mol) and tyrosinase (-53.09 kcal/mol), respectively. Kaempferitrin displayed the highest number of stable interactions with collagenase and hyaluronidase, while limocitrin-7-(6”- acetylglucoside) and isovitexin-2”-O-arabinoside interacted more with elastase and tyrosinase, respectively. The resulting complexes formed with chamaemeloside (-66.59 kcal/mol), isocarlinoside (-65.79 kcal/mol), neocuscutoside C (-41.09 kcal/mol), and aspulvinone H (-72.28 kcal/mol) against acetylcholinesterase, butyrylcholinesterase, β-secretase and monoamine oxidase, respectively, had the lowest binding free energy values compared to the respective standards. However, benzyl alcohol β-D-rutinoside, kaempferitrin, neocuscutoside C and aspulvinone H possessed the most stable interactions with acetylcholinesterase, butyrylcholinesterase, β-secretase and monoamine oxidase, respectively. The D-galactose-treated flies experienced significant distortion (p ˂ 0.05) in their antioxidant status and enzymes (catalase, superoxide dismutase and glutathione peroxidase). However, the inclusion of dry lemongrass infusion in the diet restored all the alterations witnessed in the D-galactose flies. The dry lemongrass infusion also upregulated the SOD1, CAT and dFOXO genes while downregulating the DILP2 gene. It can be concluded that both fresh and dry lemongrass infusions are rich in nutrients and phytochemicals, with the dry infusion displaying better antioxidant and anti-ageing properties in vitro. This is confirmed by the in vivo studies where the dry lemongrass infusion was more effective in ameliorating ageing-related complications in Drosophila melanogaster. Though the phytochemicals present in both teas are similar, they are more abundant in the dry tea, which may account for its more potent activities. These phytochemicals include lonicerin, chamaemeloside, kaempferitrin and neocuscutoside C. Consequent upon the outcome of this study, a ready-to-drink beverage may be developed from the dry lemongrass while its bioactive compounds are isolated for future drug development.