Biological and chemo-diverse characterization of Amazonian (Ecuador) Citrus petitgrains

Six Amazonian petitgrain samples from C. nobilis Lour., C. auran-tium L., C. limon L. and mixture of Citrus spp. (Rutaceae), named CN, CA, CL1, CL2, C1 and C2, were chemically characterized by GC-MS and ¹³C NMR and evaluated for antioxidant acitivity (DPPH and β-carotene bleaching tests), for antimicrobial properties (disk diffusion method) and for antifungal capacity (agar vapour assay). CN, C1, C2 samples evidenced the most interesting results: CN (γ-terpinene/linalool chemotype: 14.3 %/41.6 %, with a considerable amount of thymol: 9.0 %), and C1 (linalool, 18.3 %; sabinene, 11.6 %; thymol, 5.5 %), showed relevant antioxidant activity with both DPPH (IC₅₀ = 3.52 and 5.48 mg/ml, respectively) and β-carotene (IC₅₀ = 0.387 and 0.491 mg/ml, respectively). Antibacterial properties of CN and C1 against P. mirabilis (MIC = 0.61 mg/ml for both) and B. subtilis (MIC = 0.61 and 0.44 mg/ml, respectively) were most probably due to thymol. C2 (geranial: 34.7 %, neral: 33.1 %) evidenced a valuable bioactivity against C. albicans (MIC = 0.44 mg/ml). The 50 % growth inhibition (IC₅₀) of the dermatophytes T. mentagrophytes and N. cajetani was reached with amounts of C1, C2 and CN less than 4 μl/plate. Bioactivity of Amazonian Citrus spp. CN, C1 and C2 essential oils suggests their potential use as food preservatives or additives in cosmeceuticals as preventive against dermatophytic fungal infections.