OPTIMIZED EXTRACTION AND COMPREHENSIVE CHEMICAL PROFILING OF GUARANA (Paullinia cupana) SEEDS

Paullinia cupana Kunth (guaraná) is an Amazonian crop produced commercially almost exclusively in Brazil and represents an important biodiversity-based resource for the national bioeconomy. Beyond its high caffeine content, guaraná seeds contain catechin, epicatechin, and procyanidins, compounds associated with antioxidant, anti-inflammatory, metabolic, and cognitive effects [1]. However, although individual procyanidins have been identified, information on their oligomeric distribution and structural characteristics remains limited [1–3]. This study aimed to sequentially optimize the extraction of guarana bioactives and characterize the recovered procyanidin profile. Optimization was performed in successive stages. First, a water/ethanol/acetone mixture design comprising 10 solvent systems was evaluated at 45 °C, 75 min, 125 rpm, and a 1:15 solid-to-liquid ratio. Extraction yield was determined gravimetrically, while total phenolics and antioxidant activity were measured by Folin–Ciocalteu and TEAC assays. The mixture containing 36.7% water, 18.8% ethanol, and 44.5% acetone yielded 23.9 ± 2.0% extract, 149.1 ± 5.5 mg GAE/g extract, and 999.2 ± 334.8 mg Trolox/g extract. Fractional factorial screening then identified agitation, pH, solid-to-liquid ratio, extraction time, and temperature as relevant variables. Kinetic evaluation fixed extraction time at 45 min, resulting in 24.8% yield, 204.8 ± 4.5 mg GAE/g, and 1,929.0 ± 38.4 mg Trolox/g. A central composite rotatable design subsequently established 116 rpm, a 1:19.3 solid-to-liquid ratio, 46.1 °C, pH 6.13, and 45 min as the multiresponse operating condition. Validation showed relative differences of −0.4% for yield, +14.8% for total phenolics, and −25.7% for TEAC between predicted and experimental values. Chemical characterization complemented process optimization. LC-ESI-MS/MS of selected extracts detected 74 features in ESI+ and 165 in ESI−, including methylxanthines, catechin/epicatechin, caffeic acid, and A- and B-type procyanidins. Diol-phase quantification showed total DP1–DP5 contents of 227.8–257.9 mg/g extract, with DP2 ranging from 31.3 to 34.3 mg/g. Among DP2–DP5, DP3 predominated, representing 56.8–60.3% of the quantified oligomeric fraction. Phloroglucinolysis indicated low mean degrees of polymerization (mDP 1.5–1.7), with (-)-epicatechin-rich extension units (80.6–83.0%) and (-)-epicatechin representing 56.7–67.1% of initiator units. These findings establish a reproducible extraction workflow and provide complementary quantitative and structural information on guaraná procyanidins, supporting composition-oriented characterization and standardization. The final optimized condition is under LC-MS and complementary antioxidant analysis, while additional guarana batches are being compared to assess inter-batch chemical and functional variability and support sustainable guaraná valorization.

References:

[1] TORRES, E.A.F.S. et al. Compr. Rev. Food Sci. Food Saf. 21 (2022) 272. doi:10.1111/1541-4337.12862.

[2] Machado, K.N. et al. Food Chem. 239 (2018) 180.

[3] da Costa Pinaffi, A.C. et al. Molecules 25 (2020) 679.

Acknowledgment: FAPESP grants 2025/11290-7 and 2024/14698-4.