Effects of oil exploration on the anatomy and antimicrobial activity of the leaves of Annona muricata l. (Annonaceae)

Abstract

Nigeria flares much natural gas associated with oil exploration like many other countries of the world. A major problem of gas flaring is the release of large amounts of methane, which has the potential to affect medicinal plants. The effects of gas flaring on the anatomy and antimicrobial
activities of Annona muricata, used by traditional medical practitioners in the Niger Delta to treat infections was investigated. The leaves of Annona muricata Linn (Annonaceae) were collected from Ologbo, near Benin City (Edo State), Ebedei, near Abraka (Delta State) and Elele, near Port-
Harcourt (Rivers State), three towns in the Niger Delta region of Nigeria where gas flaring is still taking place. Evaluation of the anatomical sections of the leaves was carried out to determine micromorphological profile. Chemical and chromatographic tests were employed in phytochemical
investigations. Inhibitory activity of aqueous ethanol extracts against clinical strains of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Proteus mirabilis and Enterococcus faecalis were compared with that of ciprofloxacin. Microscopic studies
irrespective of place of collection showed that the leaves have anisocytic stomata arrangement. The epidermal cells were beaded and had uniseriate covering trichomes on both surfaces. The transverse section showed dorsiventral arrangement. Phytochemical screening revealed the presence of alkaloids, tannins, cardiac and cyanogenetic glycosides. The aqueous ethanol extracts inhibited the growth of Staphylococcus aureus to varying degrees. A. muricata has been reported to possess broad spectrum of antimicrobial activity. However, our findings showed a reduction of antimicrobial activity by the species growing in some parts of the Niger Delta where gas flaring is still ongoing. Concerted efforts should be made by the Nigerian Government to stop gas flaring in the region to preserve the pharmacological and biological activities of the medicinal plants.

Keywords: Annona muricata, antimicrobial, anatomical, oil exploration, gas flaring