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

Six Amazonian petitgrain samples from C. nobilis Lour., C. aurantium 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 beta-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 (alfa-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 beta-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 Candida 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 microl/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.