HPLC IDENTIFICATION AND ANTIOXIDANT ACTIVITY OF EXTRACTS FROM UNDERUTILIZED BETALAIN-RICH SPECIES (Alternanthera spp. and Bougainvillea spp.)

In recent years, there has been a growing scientific and consumer interest in Unconventional Food Plants (PANCs) since they can deliver a broad spectrum of macro and micronutrients, including phenolic compounds. While Alternanthera brasiliana (Amaranthaceae) and Bougainvillea species are primarily cultivated for ornamental or traditional medicine purposes, they represent underutilized sources of functional ingredients. Beyond their visual appeal, these plants synthesize nitrogenous betalain pigments (betacyanins and betaxanthins) alongside polyphenols with strong radical-scavenging capabilities. Consequently, they hold significant potential for culinary applications and as natural, antioxidant-rich colorants for the food industry. This research investigated the total phenolic content (TPC), individual betalain fractions, ABTS antioxidant capacity, and HPLC-DAD chromatographic profiles of aqueous extracts from A. brasiliana (AB) leaves and Bougainvillea sp. (BV) bracts. Dried samples were extracted in 0.1% trifluoroacetic acid water (1:25 g/mL) at 45 °C for 30 min and filtered. TPC was quantified via Folin-Ciocalteu assay (mg GAE/g dry leaf [DL]), while betacyanin (BC) and betaxanthin (BX) levels were measured spectrophotometrically at 538 nm and 480 nm, respectively (mg/g DL). Antioxidant efficacy was assessed using ABTS radical reduction (mmol Trolox eq./g DL), and individual phenolic constituents were profiled via HPLC-DAD. BV exhibited superior phenolic density and antioxidant capacity compared to AB (TPC: 36.37 ± 2.94 vs. 18.25 ± 2.5 mg GAE/g DL; ABTS: 72.65 ± 1.62 vs. 9.81 ± 0.66 mmol TE/g DL). Similarly, pigment accumulation was higher in BV (BC: 1.49 ± 0.03; BX: 0.90 ± 0.01 mg/g DL) than in AB (BC: 0.95 ± 0.01; BX: 0.44 ± 0.01 mg/g DL). HPLC analysis identified 32 compounds in AB, dominated by myricetin (7,583.18 mg/kg), procyanidin A2 (804.35 mg/kg), and o-vanillin (548.96 mg/kg). Whilst, BV yielded 34 compounds, characteristically rich in fumaric acid (1,236.13 mg/kg), ferulic acid (486.15 mg/kg), and myricetin (399.41 mg/kg). This study provided a comprehensive analysis of the phenolic profiles and bioactive properties of the studied PANCs as a way to create strategies for the integration of derived ingredients into food matrices. Both extracts, especially from Bougainvillea sp., demonstrated high betalain contents and antioxidant potential, with the presence of flavonoids and phenolic acids with pertinent bioactive properties. This approach reinforces the nutritional and functional value of PANCs for applications in the food and pharmaceutical industries.

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001.