*5.3. Vitamins*

Vitamin C is commonly known as ascorbic acid, and is a highly water-soluble vitamin [170]. This colorless compound has high antioxidant potential owing to its strong reducing nature [171]. The photosensitive ascorbic acid works best in a hydrophilic environment [172]. This crystalline compound is not synthesized in humans; therefore, it has to be taken in the regular diet [173]. Diets should be supplemented with vitamin C-rich sources, such as oranges, broccoli, brussels sprouts, green peppers, strawberries, kiwifruit and grapefruit, to avoid the vitamin C deficiency associated health problems like cardiovascular diseases, scurvy, and others [174]. Ascorbic acid has a high antioxidant potential and free radical-scavenging properties, which helps in preventing the oxidation of tissues, cell membranes and macromolecules (DNA and proteins) by free radicals [173].

Vitamin E is a fat-soluble membrane-bound compound which has high free radical-scavenging as well as antioxidant potential [175]. This nonenzymatic antioxidant is found in wheat germ oil, sa fflower oil, sunflower oil, vegetables, peanuts, corn, almonds, soy and meat [176]. A deficiency of vitamin E in the body may lead to the development of various health conditions in infants, such as dryness, papular erythema, depigmentation and oedema [177]. Vitamin E consumption helps in combating skin ageing symptoms due to its e fficacy in preventing the peroxidation of lipids and the cross-connection of collagen fibers [4]. Vitamin E has been proven to relieve sunburn and UV-associated skin damage [178].

Both vitamins C and E work synergistically. For instance, when UV-induced molecules oxidize the cellular constituents, a chain reaction of lipid peroxidation starts in the membrane rich in polyunsaturated fatty acids. During this, dα-tocopherol (antioxidant) gets oxidized to the tocopheroxyl radical and regenerates itself through ascorbic acid [179,180]. Di fferent food sources such as corn, seeds, vegetable oils (sunflower oil and sa fflower oil) and soy are rich in tocopherol [4]. Moreover, the consumption of vitamin E from natural sources help against lipid peroxidation and collagen cross-linking, as both are associated with skin ageing. Additionally, topically applied vitamin E has also been reported to reduce chronic UVB-induced skin damage, erythema, sunburned cells

and photocarcinogenesis [181,182]. A deficiency of vitamin E is also associated with a syndrome of edema with seborrheic changes, as well as depigmentation and dryness in premature infants [183]. Ekanayake-Mudiyanselage and Thiele, upon analyzing their study, stated that the level of vitamin E is dependent on the density of sebaceous glands in the skin. The oral supplementation of α-tocopherol for three weeks has been shown to cause a substantial increase in vitamin E levels in the sebaceous gland, especially on the face [184]. In a comparative study, the oral consumption of both vitamin C and E has been shown to improve the photoprotective e ffect in contrast to monotherapies [185]. Another study was conducted on 33 participants who received 100 or 180 mg vitamin C or placebo per day for four weeks. The result obtained from the study revealed that orally consumed vitamin C improved the radical scavenging activity of the skin by 22% (for 100 mg) and 37% (for 180 mg) from the baseline [87]. In the study by the alpha-tocopherol and beta carotene cancer prevention study group, it was found that vitamin E has insignificant e ffects on the prevention of lung cancer [164].

Nutraceuticals, functional foods and dietary supplements encompass a large group of compounds which are well known to improve health [186]. Functional foods have gained global attention owing to their impact on improving the symptoms of skin ageing [187]. Notably, fruits constitute an essential source of active metabolites used to curb skin ageing symptoms, as they are enriched with phenolic compounds, carotenoids and ascorbic acid, and possess high antioxidant potential [188]. The various plants and their components with anti-ageing potential are listed in Table 1.





## **6. Concluding Remarks**

Ageing is a complex and progressive biological process, which gets a ffected by environmental and genetic factors. Nowadays, ageing is also linked with the consumption of an imbalanced diet deficient in many essential nutrients. Lately, nutraceuticals have gained appreciation and are being considered as a crucial element in improving life and providing antioxidant-containing molecules. Various vegetables and fruits contain antioxidant molecules with beneficial properties that can help in delaying the process of ageing. Moreover, these nutraceuticals do not show unwanted symptoms; instead, they have a beneficial impact on the digestive system. Therefore, nutraceuticals as food supplements have promising potential in combating as well as delaying the ageing process. The benefits associated with nutraceuticals prompts their incorporation into the diet for health benefits and long life. The current review meticulously summarizes the anti-ageing e ffects of plant-based supplements and plant-derived metabolites. Since most of the data have been obtained in vitro, caution is advised for inferring the clinical applicability of in vitro-tested molecules. Referencing, examining and confirming the human trial data is highly recommended.

**Author Contributions:** Conceptualization, R.S. (Reena Singh) and K.K.; Manuscript writing, D.S.D. and S.B.; Manuscript editing, D.S.D., S.B., R.S. (Ruchi Sharma), K.B., D.K., C.C. and E.N.; Critical revising, R.S. (Reena Singh) and K.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the University of Hradec Kralove (Faculty of Science VT2019-2021) and Ministry of Health (No. NV19-09-00578).

**Conflicts of Interest:** The authors declare no conflict of interest.
