Abstract
The endemic Chilean edible plant Gunnera tinctoria (Nalca) is highly appreciated in the south of Chile by the small farmers. Nevertheless, no background exists about his secondary metabolites. In the present study, in the leaf from G. tinctoria was investigated the content of bioactive compounds like coumaric acid, ascorbic acid and total phenols; the antioxidant capacity was evaluated by 3-ethylbenzothiazoline-6-suslfonic acid (ABTS), oxygen radical absorbance capacity (ORAC), ferric reducing antioxidant power), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods reducing sugars were measured. Finally, the biological activity was evaluated against Cladophialophora and Cryptococcus laurentii. The results suggest that the most abundant constituent in the extract were catechin (1344.97 mg/100 g dry weight) and epicatechin (1429.28 mg/100g dry weight), and was confirmed and quantified by high performance liquid chromatografy (HPLC-PDA); while the ORAC methodology showed a high antioxidant capacity (192000.0±5.91 umol Trolox Eq/100 g dry weight). On the other hand, the extract had a fungicide effect against both microorganism assayed, inhibiting the growth of Cladophialophora´s mold- and the yeast Cryptococcus laurentii. This is the first report of antioxidant capacity, bioactive compounds and biological activity of G. tinctoria, and these findings suggest that an extract prepared from the Nalca leaf may be a promising source of antioxidant and bioactive compounds and as a research object by being an antifungal and therapeutic alternative in development. Key words: Gunnera tinctoria, Nalca, antioxidant capacity, biological activity, nutraceutical.
Highlights
The proximal physico-chemical composition of the G. tinctoria leaf is shown in Table 1, and Table 2 shows that the Nalca leaf has a significant amount of metabolites, which have been quantified as total gallic acid equivalent polyphenols
The antioxidant and reducing activity of nalca leaf extracts was characterized by different assays (ABTS, Ferric reducing/antioxidant power assay (FRAP), DPPH, Oxygen radical absorbance capacity (ORAC))
The percentage of humidity for leaf of G. tinctoria is of 90.42% being a value of water content similar to those reported for kiwi (83.98%) (Morillas-Ruiz and Delgado-Alarcón, 2012), orange (85.70%) Berlitz and Grosh (1999), mango (82.10%) (Moreiras et al, 2006), and slightly higher than those determined for avocado (72.07%) and cherry (75.84%) (Morilla-Ruiz and Delgado-Alarcón, 2012)
Summary
Flavanols like catechin and epicatechin are acknowledged for their antibacterial capacity (HamiltonMiller, 1995), anti-inflammatory activity and cancer preventives for humans (Fujiki et al, 2002), and ascorbic acid which can reduce the malignant potential of melanoma cells (Fischer and Miles, 2017). Its distribution extends to Central and Southern Africa, Madagascar, New Zealand, United Kingdom, Tasmania, Indonesia, Philippines, Hawaii, Mexico, Venezuela, Colombia, Chile and Argentina; having been reported in South America 23 species in Colombia, 12 in Chile, 7 in Ecuador, 6 in Peru, 5 in Argentina and Bolivia, 3 in Venezuela, 2 in Brazil and one in Uruguay, including Gunnera tinctoria (Mol.) Mirb., Gunnera magellanica Lam., Gunnera brephogea Linden and Gunnera manicata (Bergman et al, 1992; Wanntorp and Klackenberg, 2006)
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