## 7 Vitamins  
Vitamins are essential nutrients to ensure average growth and human health. They are a diverse group of organic compounds, classified either as water-soluble (vitamins B and C) or fat-soluble (vitamins A, D, E, and K) [80]. Vitamins have various biochemical roles, and they are already highly commercialised as nutraceutical and functional food additives [80]. Vegetables, fruits, unrefined cereals, seeds, and nuts are key sources of vitamins for humans [87]. Compared to other studied compounds, a large variety of methods are used to analyse vitamin concentrations. Hexane and ethyl acetate are commonly used solvents for the extraction of lipid-soluble vitamins. A wider variety of solvents are used for the extraction of water-soluble compounds. [PERSON] et al. [32] and [PERSON] et al. [5] use the extraction and analytical methods proposed by [PERSON] et al. [88] for fat-soluble and water-soluble vitamins. Various HPLC methods involving a photodiode array detector (PDA) or fluorescence detector (FL) are widely used; only [PERSON] et al. [89] use a DAD and [PERSON] et al. [90] an ultraviolet (UV) detector in their analytical methods. Ascorbic acid (vitamin C) is an essential nutrient for humans and other animals. Humans cannot synthesise vitamin C, and deficiency due to insufficient intake can cause scurvy disease [80,87]. It has also been reported to help maintain the integrity of cellular membranes and improve skin health [84,85]. It is a co-factor for enzyme reactions and a potent antioxidant which has been shown to have a preventive effect on various chronic conditions [91]. It has also been reported to improve skin health [84,85]. Ascorbic acid degrades relatively fast, and a study by [PERSON] et al. [22] showed a gradual decrease in the ascorbic acid content of _Salicornia bigelovii_ during storage: 56% of ascorbic acid was lost after eight days at 0 \({}^{\circ}\)C. The succulent _Amaranthaceae_ family halophytes _Arthrocnemius indium_, _Halconneum strobilaceum_, and _Salicornia bigelovii_ have been found to be rich in ascorbic acid [22,90]. [PERSON] et al. [84] also found considerably high amounts of vitamin C from _Salvadora persica_ fruit. [PERSON] et al. [85] also suggest that the ascorbic acid content in _Thepesia populnea_ leaves is enough to fulfil the daily requirements of a healthy individual. Compounds considered as B complex vitamins are antioxidants and essential co-enzymes, supporting vital biological processes [80,89]. For example, thiamine (B1) is essential to carbohydrate metabolism, pyridoxine (B6) to protein metabolism, folate (B9) to the synthesis of nucleic acids, and cobalamin (B12) for the nervous system, cell growth, and bone health [5, 89]. [PERSON] et al. [89] developed an optimised analytical method to measure the vitamin in B complex in halophyte extracts and suggested that _Suada aegyptiaca_ and _Suada vera_ may be promising sources for the production of health-beneficial products for food and pharmaceuticals. _Suada aegyptiaca_, in particular, was found to be a significant source of cobalamin [89], with concentrations being higher than in sea buckthorn [92], making it desirable for people following a strictly plant-based diet and who are at risk of vitamin B12 deficiency. The amounts of water-soluble vitamins (vitamin C and B complex vitamins) found in the biomass of various halophytes are summarised in Table 5.  
Tocopherols (vitamin E) are lipid-soluble antioxidants, and their radical scavenging activity protects cell membranes, lipoproteins, and other molecules against lipid peroxidation caused by oxidative stress [6, 11]. Improved cardiovascular health, prevention of degenerative disorders, and anti-cancer properties are also reported as potential health benefits of tocopherods [80]. Tocopherols are present in different isomers, \(\alpha\)-tocopherol being reported as the most abundant in halophyte biomasses [11]. [PERSON] et al.