Fig. 4From: Antibacterial and antioxidant properties of humic substances from composted agricultural biomassesAntioxidant activity of humic substances (HS) extracted from artichoke (CYN), coffee grounds (COF), and pepper (PEP) composted residues, as measured by ABTS assay (a), and Folin–Ciocalteu method (b). Vertical bars represent the standard deviation. Different capital letters indicate significant differences according to Tukey test (p ≤ 0.05)Back to article page