In-vitro Biochemical Screening of Antimicrobial Activity of Locally Derived Plant Extracts from Lagos State Against Multi-Drug Resistant Bacteria

In-vitro Biochemical Screening of Antimicrobial Activity of Locally Derived Plant Extracts from Lagos State Against Multi-Drug Resistant Bacteria

Abstract

The rapid rise of multi-drug resistant (MDR) bacteria has emerged as a critical global health challenge, highlighting the urgent need for alternative antimicrobial agents. This study evaluates the in-vitro biochemical properties and antimicrobial activity of locally sourced plant extracts from Lagos State against selected MDR bacterial isolates. Fresh leaves and bark of commonly used medicinal plants were collected, air-dried, and extracted using methanol and aqueous solvents. We performed phytochemical screening to identify alkaloids, flavonoids, tannins, saponins, terpenoids, and phenolic compounds.

The extracts’ antimicrobial activity was tested against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae using the agar well diffusion method. We also determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) to quantify their potency. Results indicated that methanol extracts contained high levels of bioactive compounds and exhibited significant antimicrobial activity. Some extracts produced inhibitory zones comparable to standard antibiotics. Overall, the findings suggest that Lagos State’s indigenous plants contain potent bioactive compounds capable of combating antibiotic-resistant bacteria, justifying further biochemical and mechanistic investigations.

Keywords: medicinal plants, antimicrobial activity, multi-drug resistance, phytochemicals, Lagos State, in-vitro screening.

CHAPTER ONE

1.0 Introduction

Antimicrobial resistance (AMR) presents a major threat to public health worldwide. Multi-drug resistant (MDR) bacteria have made many conventional antibiotics less effective, creating a pressing need for alternative treatment options. In Nigeria, frequent misuse of antibiotics and limited healthcare access contribute to rising resistance rates. This situation emphasizes the importance of exploring medicinal plants, which have historically provided bioactive compounds capable of inhibiting microbial growth.

Lagos State, with its diverse flora, offers a rich source of medicinal plants traditionally used to treat infections. These plants contain phytochemicals such as alkaloids, flavonoids, terpenoids, tannins, and phenols. Evidence shows that these compounds interfere with bacterial cell membranes, inhibit enzymes, and disrupt protein synthesis. Thus, scientific evaluation of these plants’ antimicrobial potential can support the development of novel therapeutic agents.

1.1 Background of the Study

MDR bacteria such as E. coli, S. aureus, K. pneumoniae, and P. aeruginosa increasingly resist common antibiotics, posing severe challenges to health systems. The World Health Organization (WHO) predicts that infections currently treatable with antibiotics may become fatal if new antimicrobial sources are not identified. Medicinal plants, widely utilized in Nigeria’s traditional medicine, represent a largely untapped resource. Lagos State markets provide abundant access to such plants, yet their biochemical composition and antimicrobial efficacy remain inadequately documented.

Phytochemicals like flavonoids, tannins, and saponins exhibit antibacterial properties by damaging cell walls and inhibiting microbial metabolism. Their study not only validates traditional uses but also opens pathways for developing safer, plant-based antimicrobial agents, especially in regions with limited healthcare access.

1.2 Statement of the Problem

Despite widespread reliance on herbal remedies, few studies have validated their effectiveness against MDR bacteria. Lagos State markets offer numerous herbal products with undocumented biochemical profiles, and antibiotics misuse continues to drive resistance. This gap necessitates systematic in-vitro biochemical evaluation of locally derived plants to determine their antimicrobial potential and guide future drug discovery.

1.3 Aim and Objectives

Aim:
To evaluate the in-vitro biochemical properties and antimicrobial activity of selected medicinal plant extracts from Lagos State against multi-drug resistant bacteria.

Objectives:

1. Conduct phytochemical screening of selected medicinal plant extracts.

2. Assess antimicrobial activity against MDR bacterial strains.

3. Determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of active extracts.

4. Compare the efficacy of plant extracts with standard antibiotics.

1.4 Research Questions

1. Which locally derived plant extracts contain active phytochemicals?

2. How effective are these extracts against MDR bacterial strains?

3. What are the MIC and MBC values of the most potent extracts?

4. Can these plant extracts serve as alternatives or adjuncts to conventional antibiotics?

1.5 Significance of the Study

This study provides scientific evidence supporting the antimicrobial efficacy of local plant extracts. It guides future drug discovery, validates ethnobotanical knowledge, and contributes to strategies for reducing antibiotic dependence and controlling MDR bacterial infections.

1.6 Scope of the Study

The study focuses on in-vitro evaluation of methanolic and aqueous extracts from selected medicinal plants collected from Lagos State markets. MDR strains of E. coli, S. aureus, P. aeruginosa, and K. pneumoniae were tested. The study emphasizes phytochemical characterization and antimicrobial screening rather than in-vivo toxicity or clinical trials.

1.7 Definition of Terms

• Phytochemicals: Plant-derived compounds with biological activity.

• Antimicrobial activity: The ability of a substance to inhibit or kill microorganisms.

• Minimum Inhibitory Concentration (MIC): Lowest concentration of a compound that prevents visible microbial growth.

• Multi-Drug Resistant (MDR) Bacteria: Microorganisms resistant to at least one antibiotic in three or more categories.

• Extracts: Solutions obtained by dissolving plant constituents in solvents.