Acid cactus fruits “xoconostle” have been used since the pre-Columbian period as a treatment against diverse diseases. In this study, bioactive compounds (phenols and flavonoids) and the in vitro inhibition effect against α-amylase and α-glucosidase were evaluated. Four different extracts of cactus acid fruits were prepared from (1) endocarp, (2) mesocarp, (3) pericarp and (4) whole fruit (WFE). The results showed significant differences (p < 0.05) between extracts. Pericarp extracts had 2.23 ± 0.01 mg of gallic acid equivalents per gram GAE/g of phenol content and 0.84 ± 0.14 mg quercetin equivalents per gram QE/g flavonoid content, while WFE presented 1.52 ± 0.04 mg GAE/g and 0.84 ± 0.14 mg QE/g; however, the inhibition of α-amylase and α-glucosidase were higher with WFE. It was found by using 25 mg/mL of WFE an α-amylase inhibition of 63. ± 1.53% and with 30 mg/mL of WFE an α-glucosidase inhibition of 46.5 ± 1.45% after simulated intestinal conditions. The WFE could be used as a therapeutic strategy in controlled diets of diabetic patients due to its low cost, natural origin, and effect after simulated intestinal conditions.