Zanthoxylum zanthoxyloides and Zanthoxylum leprieurii: a micromorphological, phytochemical and antibacterial evaluation

• Articles in SCI Journals
• Jun, 2019

Summary:

Introduction: The biosynthesis of a large diversity of secondary metabolites, that includes terpenic compounds, alkaloids, flavonoids and phenolics, is one of the most relevant adaptive mechanism presented by plants in order to survive on harsh environment. The objective of this work was to carry out preliminary studies on micromorphology, phytochemical profile and antibacterial activity of two Rutaceae species, native to Guinea-Bissau, Zanthoxylum zanthoxyloides and Z. leprieurii. Both species are currently used as medicine and their antimicrobial properties, among others, are reported in the regions of their geographical distribution.

Materials and methods: Plant material was collected in Guinea-Bissau during 2016–2017. Plant identification was confirmed and vouchers deposited at LISC. Leaves were subject to the usual procedures for light and scanning electron microscopy studies [1]. For anatomical studies the plant material was processed with the paraffin micro technique [2]. Extracts were obtained by a sequential extraction of the dry plant powder with n-hexane, CH₂Cl₂, EtOAc, MeOH and water, filtered, concentrated and stored at −20ºC. Evaluation of the semi quantitative phytochemical profile was carried out thought TLC on silica gel, developed with appropriated solvents. Spots were revealed with proper revelators, according to Wagner and Bladt [3]. The extracts were tested against six Gram-positive bacteria: Staphylococcus aureus (ATCC 6538, 43866, CIP 106706) S. epidermidis(ATCC 12228) and Enterococcus hirae (CIP 5855) and two Gram-negative Pseudomonas aeruginosa (ATCC 9027) and Escherichia coli (ATCC 8739). The minimum inhibitory concentrations (MIC) were determined by the serial broth microdilution method. The MIC values were considered negative when >100 μg/mL.

Results: The micromorphological characteristics of both species leaves were carried out and similar outcomes were found: i) polyhedral epidermal cells on the upper and lower leaf surfaces; ii) hypostomatic leaves; iii) internal secretory structures with a lipid nature. The most significant differences were the leaves thickness, thinner in Z. leprieurii and the large internal secretory structures and idioblasts with druse type calcium oxalate crystals, in the parenchyma cells of this same species. The extracts of leaves and roots, with increasing polarities, were prepared and their antibacterial activity against the reference bacteria were evaluated. The extracts with the highest activity were the most apolar Z. leprieurii leaves extracts, which were able to inhibit the growth of E. hirae and all the Staphylococcus strains assayed, including the resistant ones, with MIC between 15–60 µg/mL

Discussion and conclusions: These are preliminary results that allow species differentiation and point to the validation of their use in traditional medicine and emphasize the worthwhile of additional studies.

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https://www.tandfonline.com/doi/abs/10.1080/07853890.2018.1561716