Potential of Agave spp. in Thailand as an alternative prebiotic sweetener: optimization of prebiotic extraction and functional evaluation of agave syrup

Agave is a drought-resistant plant commonly used as an ornamental in Thailand. Despite its potential, the applications of agave remain limited. This research optimized extraction of fructo-oligosaccharides (FOSs) from the agave tuber, by comparing the extraction methods (aqueous, ethanol, and co-extraction) under various conditions. The components and structure of agave extract were investigated. Based on the results, ethanol extraction was the most effective method, yielding the highest fructose polymers (3.03% (w/v)) under 75% (v/v) ethanol at an agave powder-to-ethanol ratio of 1:5 at 75 °C for 24 h, containing short-chain FOSs with a degree of polymerization (DP) less than 10; 1-kestose (DP3), nystose (DP4), and 1-fructofuranosyl-D-nystose (DP5) and various sugars, especially fructose. The concentrated agave extract syrup (67°Brix) composed of FOSs (5.05% (w/v)), sugars (62.43% (w/v)), and phenolic compounds (2.76 mg GAE/mL) with antioxidant properties (59.61% of inhibition, IC50 of 2.84 mg/mL in DPPH assay). Additionally, agave extract syrup acted potentially prebiotic properties to resist enzymatic digestion in gastrointestinal tract under in-vitro with lower digestion (3.5%) compared to cane syrup (6.0%) including to promote and prolong the growth of probiotic Lactobacillus casei TISTR 1463. Furthermore, its estimated glycemic index and hydrolysis index (eGI=49.20; HI=17.29) were markedly lower than cane syrup (eGI=60.34; HI=37.57) under i n-vitro condition. Based on acute toxicity, agave powder and agave extract syrup were confirmed with no toxicity in rats. These findings highlight the potential of agave tubers as a valuable agricultural resource for production of high-value agave-derived products, particularly the functional ingredients and low-GI prebiotic sweeteners.