Spectrophotometric Determination of Anthocyanin Content in Six Common Vegetables

Ma. Jamica Trexy M. Espinosa

Abstract

Anthocyanins are flavonoids that render the red, orange, purple, magenta, and blue colors in leaves, flowers, and fruits in plants. Anthocyanins are known as protective agents against diseases and have potential antioxidant, anti-inflammatory, and anticarcinogenic properties. Fresh samples of sweet potato/camote (Ipomoea batatas, Convolvulaceae), vegetable amaranth (Amaranthus tricolor, Amaranthaceae), and sessile joyweed/lupo (Alternanthera sessilis, Amaranthaceae) tops/talbos; yardlong bean/sitaw (Vigna sesquipedalis, Fabaceae), and winged bean/balagay (Psophocarpus tetragonolobus, Fabaceae) immature pods, and pigeon pea (Cajanus cajan, Fabaceae) seeds were obtained from different markets in Iloilo city to determine the amount of anthocyanins using UV-Visible spectrophotometry. The species morphotypes used for this study have purple pigmentation in leaves/tops, pods and seeds. Sample extracts in 2% HCL and citrate buffer showed various reactions. Using 2% HCL color changed to brownish orange for camote, to light brownish orange for kolitis, pale orange for balagay, magenta to red violet for lupo, crimson for kadios, lighter crimson for sitaw; while sample extracts with citrate buffer appeared to be almost colorless. In terms of color intensity, for camote, kadios, sitaw and balagayextracts in 2% HCL produced darker color compared with those in citrate buffer. In contrast, kolitis and lupo generated darker color in citrate buffer. Based on the total anthocyanin content (TAC) expressed as µg/g cyanidin, values presented as the average of three replicates, plant samples were ranked in increasing order amaranth (-1.25±0.1) < lupo (-6.98±0.1) < balagay (5.68±0.6) < camote (6.57±0.3) < sitaw (18.2±0.1) < pigeon pea (50.6±1.1). The negative values for lupo and amaranth might indicate the absence of anthocyanin but may contain another type of pigment considering that both extracts showed darker color in the citrate buffer compared in 2% HCL solution in contrast to the other four samples.