Betalains and phenolic compounds of leaves and stems of Alternanthera brasiliana and Alternanthera tenella

Abstract

Betacyanins and phenolic compounds from acetonitrile:acidified water extracts of Alternanthera brasiliana and Alternanthera tenella were characterized and quantified using a high-performance liquid chromatography system coupled with diode array and electrospray mass spectrometry detection. Four betacyanins (amaranthine, isoamaranthine, betanin and isobetanin) were tentatively identified and quantified. Twenty eight phenolic compounds of four different families (hydroxybenzoic and hydroxycinnamic acids, flavones and flavonols) were separated and characterized on the basis of their accurate MS and MS/MS information out of which ten compounds were confirmed by authentic standards. These plant species could be considered as an especially rich source of natural bioactive compounds and potential food colorants. A. brasiliana showed the highest betacyanin and polyphenols content (89μg/g and 35,243μg/g, respectively). Among polyphenols, flavonols were the more abundant (kaempferol-glucoside, kaempferol-rutinoside and kaempferol-rhamnosyl-rhamnosyl-glycoside). Meanwhile, A. tenella showed a different polyphenols profile with flavones as major compounds (glucopyranosil-vitexin and vitexin). As a novelty, pentosyl-vitexin and pentosyl-isovitexin were detected for the first time in Alternanthera plants. Both A. brasiliana and A. tenella leaves showed high total polyphenol content and in vitro antioxidant activity (FRAP). These results provide an analytical base concerning the phenolic and betalains composition and the antioxidant properties of two members of the promising Alternanthera gender, for subsequent applications, such as functional food ingredients.

Betalains in Some Species of the Amaranthaceae Family: A Review

“…Amaranthaceae family is characterised by its diversity in secondary metabolites: essential oils, sesquiterpenes, diterpenes, triterpenes, phenolic acids, flavonoids and betalains [ 67 ]. This family includes diverse genera in which betalains have been reported: Alternanthera , Amaranthus , Beta , Chenopodium , Celosia and Gomphrena [ 27 , 29 , 68 , 69 , 70 ].…”

“…Many species of Alternanthera have been used in folk medicine for the treatment of infections, genital inflammation and fever [ 84 , 85 , 86 ]. Alternanthera brasiliana (L.) Kuntze and Alternanthera tenella Colla are native to tropical and sub-tropical regions of Australia and South America [ 69 ].…”

“…These findings were generally attributed to the phenols, terpenes and sterols present in the leaves and not to their pigments or betalains. Such does not mean the absence of activity of these secondary metabolites, only very few works can be found that aimed to study the betalains of leaves from A. brasiliana [ 69 ]. The antimicrobial activity of A. brasiliana extracts on several microorganisms ( Staphylococcus aureus , S. epidermidis , Escherichia coli , Bacillus subtilis , Micrococcus luteus , Candida albicans and Saccharomyces cerevisiae ) was weak [ 94 , 95 ].…”

Development and validation of an analytical method for quantification of total flavonoids in Alternanthera brasiliana by ultraviolet-visible absorption spectrophotometry

“…Glycosylated flavonoids (Brochado et al, 2003), oxylipines (Trapp et al, 2015), alkaloids and triterpenoids (Anunciação, 2012) were isolated from the leaves. From the leaves and stalks, flavones, flavonols, steroids, betalains, betacyanins, betaxanthines, hodroxybenzoic acid derivatives and hydroxycinnamic acids has already been reported (Deladino et al, 2017).…”

“…Flavonoids are the main biologically active compounds present in A. brasiliana, so they were selected in this study to develop and validate analytical methodology for their quantification in samples of this species (Deladino et al, 2017). The importance of validating procedures for analytical safety and obtaining reliable results is known.…”