Total phenolic content is associated with antioxidant activity independently of preliminary toxicity in medicinal plants from Sinaloa, Mexico: a multivariate approach

The medicinal flora of the state of Sinaloa, Mexico, is widely used by rural and highland communities; however, scientific information regarding its phytochemical profile, antioxidant capacity, and toxicological safety remains scarce and fragmentary. The present study evaluated the relationship among the qualitative phytochemical profile, total phenolic content (Folin–Ciocalteu), in vitro antioxidant capacity (DPPH, ABTS, and FRAP), and preliminary toxicity ( Artemia salina lethality assay) of 20 ethanolic extracts obtained from 15 native medicinal species, using an integrative multivariate statistical approach (Spearman correlation, hierarchical clustering, FAMD, PLS, and PERMANOVA). A very strong positive association was found between total phenolic content and antioxidant activity (ρ = 0.72–0.92; adjusted p < 0.005), consistently confirmed across all analytical approaches. Because the Folin–Ciocalteu assay quantifies total reducing capacity rather than phenolic compounds exclusively, this association is interpreted as a quantitative relationship between reducing power and radical-scavenging activity rather than as evidence of a specific structural class. In contrast, qualitative phytochemical screening showed no predictive capacity for antioxidant activity (η² < 0.05; PERMANOVA, R 2 ≤ 0.033). The Arbutus bicolor and Eysenhardtia polystachya extracts were identified as those with the highest antioxidant potential. Preliminary toxicity and antioxidant activity exhibited functional independence (ρ ≈ 0). The data obtained for A. bicolor constitute the first quantitative evidence of antioxidant capacity and preliminary toxicity for this species native to the Sierra Madre Occidental. The multivariate approach employed provides a replicable analytical framework for the systematic exploration of regional medicinal flora and identifies A. bicolor and E. polystachya as priority candidates for chromatographic characterization (HPLC-DAD, LC–MS/MS).