Plant extracts as potential bioactive food additives

Plant extracts have potential as food additives. In this sense, this work aimed to study the bioactivities of plant extracts and their ability as health-promoting additives. Lavender, lemon balm, basil, tarragon, sage, and spearmint dry aerial parts were mechanically ground. Three extraction methods were tested: infusion and decoction, using distilled water as solvent and a sample/solvent ratio of 1:100; and hydroethanolic extraction, using ethanol 80% (v/v) as solvent and a sample/solvent ratio of 1:60. The extracts obtained were evaluated for their antimicrobial and antifungal activities, by a microdilution method. The antioxidant activity was evaluated through the lipid peroxidation inhibition assay (TBARS) and the oxidative haemolysis inhibition assay (OxHLIA). Cytotoxic activity was evaluated in tumour and non-tumour cell lines using the sulforhodamine B method, and anti-inflammatory activity in lipopolysaccharide-activated RAW 264.7 macrophages by the ability to inhibit NO production. The results showed that all extracts exhibited antimicrobial activity against six pathogens tested (MIC ≤ 2 mg/mL) and antifungal capacity against, at least, five fungi (MFC ≤ 1 mg/mL). In the TBARS evaluation, lemon balm infusion (125±2 μg/mL) and hydroethanolic extracts of spearmint (132±5 μg/mL) and lavender (177±4 μg/mL) presented the highest activities. In the OxHLIA assay, sage decoction (8.9±0.4 μg/mL) and hydroethanolic extracts of spearmint (12.5±0.2 μg/mL) and lemon balm (13.5±0.4 μg/mL) showed the best capacities to inhibit oxidative haemolysis. Regarding the anti-inflammatory activity, only the extracts of spearmint and basil, and the decoction and hydroethanolic extracts of tarragon, showed promising results (GI50<89 μg/mL). As for the cytotoxicity assay, most extracts (except those of tarragon and the infusion and decoction of basil) revealed anti-proliferative capacity in the AGS, CaCo, and HeLa tumour lines (GI50<400 μg/mL). These outcomes provide insight on the bioactivity of numerous herbal extracts, emphasising their value as food additives to prevent spoilage and deliver beneficial health effects.