Anthocyanins from Oxalis triangularis as potential food colorants

Anthocyanin pigment content and profile from Oxalis triangularis (oxalis) was investigated for the first time. The pigments were extracted, purified using C-18 resin and characterized by HPLC, UV-visible spectral analysis, physicochemical reactions, and mass spectrometry before and after alkaline and acid hydrolysis. Monomeric anthocyanin content was 195 mg/100 g leaves on malvidin-3,5-diglucoside basis. Colour characteristics of a pH 3.5 oxalis anthocyanin extract (optical density of 0.3, 520 nm) were 86.0, 9.8 and 8.0 for Hunter CIE L*, hue angle and chroma, respectively. Three anthocyanins represented 90% of the total peak area obtained by HPLC. The major anthocyanin was malvidin-3-rutinoside-5-glucoside and the others were acylated derivatives containing one and two molecules of malonic acid esterified to the main structure. The attractive hue, high anthocyanin content and edible character of O. triangularis make it a potential desirable source of natural colorant.