Bioactive compound recovery from Agave angustifolia Haw. leaf waste from bacanora industry: physicochemical properties, antioxidant and antimicrobial activity of the extract

The leaves of Agave angustifolia Haw. represent approximately 46% of the plant’s total weight, and are typically discarded during the bacanora production process in the state of Sonora, Mexico, constituting an agro-industrial by-product that is not used in the region. The leaves contain active compounds that can be extracted and used for various purposes. The objective of this research was to efficiently use the leaves of Agave angustifolia Haw. discarded during the bacanora production process. Three extraction methods were used, two fresh extractions and one from the dry material. The first involved crushing the material in water, followed by filtering and drying. The second method included an additional step of carbohydrate precipitation using absolute ethanol. The third extraction was by mashing from the dried and crushed plant material. Aqueous extraction of the dried plant material was identified as having the highest extraction yield, achieving a dry basis yield of 31.89% (w/w). The study focused on the optimization of this extraction process, considering factors such as temperature, extraction time, and the mass-to-solvent ratio, in order to contribute to the revaluation of this agro-industrial by-product. Optimal yield was achieved at 80 °C and using 30 mL of water per gram of plant material. The mineral content was 20%, with potassium and calcium accounting for 33.43% and 13.27% of the extract ash, respectively. The extract presented a dilatant rheological behavior, and its viscosity was low, evidencing that the polymeric chains are short. The extract showed significant antioxidant activity. The IC50 values were 480 µg/mL for DPPH• and 19 µg/mL for ABTS•⁺ radicals. Its reducing power determined by FRAP was 2.70 mmol TE/g. Additionally, the extract contained a total phenol content of 344.99 mg GAE/g. For antimicrobial activity, the IC50 values were 81.32 mg/mL for Listeria monocytogenes and 162.86 mg/mL for Pseudomonas fragi. Moreover, the growth of Colletotrichum siamense fungus was completely inhibited at concentrations ranging from 0.06 to 1.0% (w/v). This extract can be used for a variety of purposes, such as in the food or materials field, and its production process is easily reproducible because no complex technological processes or costly or aggressive solvents are used.