Background: Prosopis farcta belongs to the family of Fabaceae and is of ethnomedicinal value but its agricultural potential is not sufficiently explored. 

Objectives: To assessed antioxidant capacity and biostimulant activity of a P. farcta fruit extract on basil (Ocimum basilicum L.) grown under different soil-moisture levels was tested. 

Methodology: A 4×2 factorial experiment with five replications was conducted using the pot method and varying the concentration of extracts (0, 0.5, 1.0 and 2.0 g L–1) in combination with soil-moisture levels (100% and 60% field capacity). Results: Dry-extract yield was 18.6 ± 0.8%. The total phenolic and flavonoid contents were of 82.4 ± 2.7 mg GAE g-1 and of 36.8 ± 1.9 mg QE g-1 dry extract, respectively. DPPH radical-scavenging activity reached 71.3 ± 2.1% at 1.0 g L⁻¹, with an IC₅₀ of 0.42 ± 0.03 g L⁻¹. Extract concentration and irrigation main effects were significant with regard to growth, water status pigment status, oxidative stress and soluble protein as determined by two-way ANOVA (p<0.001). None of the interactions between treatments was significant for growth, SPAD, relative water content or soluble protein; except H₂O₂ (F₃,₃₂ = 7.34, p<0.001). At 60% FC, biomass and the amount of soluble protein was descriptively greater, while H₂O₂ was descriptively lower, than the untreated control, and post hoc comparisons on those data were not examined. 

Conclusion: This extract demonstrated some initial promise as a botanical biostimulant however, replication, field testing, toxicity and food-safety evaluation are needed before further recommendations.