Phytochemical investigation of Aloe pulcherrima roots and evaluation for its antibacterial and antiplasmodial activities.

Dele Abdissa,Girma Geleta,Ketema Bacha,Negera Abdissa,Horacio Bach

doi:10.1371/journal.pone.0173882

Abstract

Medicinal plants with documented traditional uses remain an important source for the treatment of a wide range of ailments. Evidence shows that majority of the Ethiopian population are still dependent on traditional medicine. Aloe pulcherrima Gilbert & Sebsebe is one of the endemic Aloe species traditionally used for the treatment of malaria and wound healing in central, Southern and Northern part of Ethiopia. The aim of the current study was, therefore, to isolate active compounds from roots of A. pulcherrima and evaluate for their antibacterial and antiplasmodial activities using standard test strains. Bioassay-guided sequential extraction and column chrom-atographic separation were employed for the isolation of bioactive pure compounds. The structures of the compounds were determined by 1D and 2D NMR spectro-scopic techniques. Disk diffusion method was employed to evaluate the antibacterial activities of the isolated compounds against four bacterial strains specifically (Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Escherichia coli ATCC 35218, Pseudomonas aeruginosa ATCC 27853). The malaria SYBR Green I-based in vitro assay technique was used for in vitro antiplasmodial activity evaluation of the compounds against chloroquine resistant (D6) and -sensitive (W2) strains of P. falciparum. Three compounds, chrysophanol, aloesaponarin I and aloesaponarin II were isolated from the acetone extracts of roots of A. pulcherrima. Evaluation of antibacterial activities revealed that aloesaponarin I and aloesaponarin II had significant activities against all the bacterial strains with inhibition zone diameters ranging from 18–27 mm as compared to the reference drug (gentamicin), which displayed inhibition zone diameter ranging between 20 mm (B. subtilis) and 25 mm (P. aeruginosa). The isolated compounds showed moderate in vitro antiplasmodial activity against both chloroquine resistant (W2) -sensitive (D6) strains. Isolation of chrysophanol, aloesaponarin I and aloesaponarin II from roots of A. pulcherrima is the first report of its kind. The finding could be used for further comprehensive evaluation of the isolated compounds for their antibacterial and antimalarial activities besides consideration of the same for potent drug development.

Highlights

Medicinal plants represent the oldest and remain an indispensable source of novel and effective pharmaceuticals
Mueller Hinton agar and nutrient broth were used for antibacterial activity test while Indochina W2 and the Sierra Leone D6 Plasmodium falciparum strains were used for antiplasmodial activity test
Of the four solvents used for extraction of the air dried roots of A. pulcherrima, acetone resulted in good extraction product, and the acetone extract showed superior antibacterial activity (S1 Table, to be discussed in details in the later section)

Summary

Introduction

Medicinal plants represent the oldest and remain an indispensable source of novel and effective pharmaceuticals. The advent of phytochemistry and pharmaceutical chemistry has enhanced the ability to utilize active compounds isolated from plants, or their synthetic equivalents in medicine. Because of long history of their safe use and good source of therapeutic agents applicable in traditional medication, searching for alternative potent antimicrobial substances from natural products is justifiable alternative approach for the control of many infectious diseases [3,4, 6] This has to be supported by wise use of the available commercial drugs in order to minimize the development of new drug resistant strains associated with drug misuse

Objectives

Methods

Results