Maca, Lepidium meyenii Walpers (Brassicaceae), is an annual herbaceous plant native to the high plateaus of the Peruvian central Andes. Its underground storage hypocotyls have been a traditional medicinal agent and dietary staple since pre-Columbian times. Reported properties include energizing and fertility-enhancing effects. Published reports have focused on the benzylalkamides (macamides) present in dry hypocotyls as one of the main bioactive components. Macamides are secondary amides formed by benzylamine and a fatty acid moiety, with varying hydrocarbon chain lengths and degree of unsaturation. Although it has been assumed that they are usually present in fresh undamaged tissues, analyses show them to be essentially absent from them. However, hypocotyls dried by traditional Andean postharvest practices or industrial oven drying contain up to 800μgg(-1) dry wt (2.3μmolg(-1) dry wt) of macamides. In this study, the generation of macamides and their putative precursors were studied during nine-week traditional drying trials at 4200m altitude and in ovens under laboratory conditions. Freeze-thaw cycles in the open field during drying result in tissue maceration and release of free fatty acids from storage and membrane lipids up to levels of 1200μgg(-1) dry wt (4.3μmolg(-1) dry wt). Endogenous metabolism of the isothiocyanates generated from glucosinolate hydrolysis during drying results in maximal benzylamine values of 4300μgg(-1) dry wt (40.2μmolg(-1) dry wt). Pearson correlation coefficients of the accumulation profiles of benzylamine and free fatty acid to that of macamides showed good values of 0.898 and 0.934, respectively, suggesting that both provide sufficient substrate for amide synthesis during the drying process.

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Purpose The purpose of this paper is to study the ability of commercial tara powder to convert rust into iron tannate and evaluate their use as raw material for the formulation of water based rust converter. Design/methodology/approach Water-borne acrylic primers were formulated with tara powder and aqueous tara extract and applied on steel rusted by three different methods. The conversion of rusted steel by tara tannins was studied by X-ray diffraction spectroscopy, infrared spectroscopy and scanning electron microscopy. The acrylic primers, containing hydrolysable tannins, were coated with alkyd finish and were evaluated in comparison to commercial systems in accelerated corrosion tests. The corrosion inhibition effects of tara powder on mild steel in 0.1M NaCl were studied by DC electrochemical techniques. Findings Tara tannin converts rust to ferric tannate and increases the magnetite content of rusted steel. The water-based acrylic primer formulated with aqueous extract of tara, alkyd-coated finish, showed performance equivalent to pure alkyd system. Research limitations/implications The chlorides content in the commercial tara powder can be screened the beneficial effect of hydrolysable tannins to convert rust. Furthermore, the water-based rust converter formulated with acrylic resin may be sensitive to salt contamination of rust. Originality/value Hydrolysable tannins from commercial tara powder have not been studied yet in its application to the development of rust converters. A water-based primer formulated with commercial tara powder developed for the effective treatment of rusted surfaces can be of interest as an environmentally friendly to current commercial approaches.