COMPARISON BETWEEN AQUEOUS AND ETHANOLIC EXTRACTS OF VERNONIA AMYGDALINA ON FUNGAL AND BACTERIAL ISOLATE FROM SPOILED PEPPER AND TOMATO FRUIT IN DUTSE JIGAWA STATE

ABSTRACT

Post-harvest spoilage of fruits, particularly tomatoes and peppers, poses significant challenges to food security and economic sustainability in Nigeria. This study investigated the comparative antimicrobial efficacy of aqueous and ethanolic extracts of Vernonia amygdalina against microbial isolates from spoiled tomato and pepper fruits in Dutse, Jigawa State. Microbial analysis revealed high contamination levels, with predominant bacterial isolates including Escherichia coli and Salmonella spp., and fungal isolates such as Aspergillus niger and Rhizopus stolonifer. The microbial load in tomatoes was slightly higher than in peppers. The antimicrobial activities of the extracts were evaluated using the agar well diffusion method. Ethanolic extracts of Vernonia amygdalina exhibited significantly greater zones of inhibition against both bacterial and fungal isolates compared to aqueous extracts. For instance, ethanolic extracts showed a zone of inhibition of 20.5 mm against Escherichia coli and 18.6 mm against Aspergillus niger, whereas aqueous extracts exhibited lower activity. The superior efficacy of ethanolic extracts is attributed to their ability to extract a broader range of bioactive compounds, including flavonoids, tannins, and alkaloids, which possess strong antimicrobial properties. The findings underscore the potential of Vernonia amygdalina ethanolic extracts as natural preservatives, offering a sustainable and eco-friendly alternative to synthetic chemicals for controlling microbial spoilage in perishable fruits. This study highlights the importance of improving post-harvest handling practices and leveraging plant-based antimicrobials to enhance food preservation and reduce losses. Recommendations include promoting the use of ethanolic extracts of Vernonia amygdalina in local food preservation strategies and conducting further research on their safety and commercial scalability. This study provides valuable insights into sustainable approaches for addressing spoilage-related challenges in agricultural produce.

 

CHAPTER ONE

INTRODUCTION

1.1 Background to the Study

Plant-based antimicrobial agents have gained significant attention in recent years due to the rising global concern about antibiotic resistance and the need for safer, more sustainable solutions in food preservation and health. Vernonia amygdalina, commonly known as bitter leaf, is a widely distributed plant in tropical and subtropical regions of Africa, renowned for its medicinal properties and potential as a natural antimicrobial agent (Igwe et al., 2021). The plant has been traditionally used to treat a variety of ailments, ranging from gastrointestinal disorders to bacterial infections, owing to its bioactive compounds such as saponins, flavonoids, and alkaloids (Nnamani et al., 2020). These phytochemicals exhibit antimicrobial, antioxidant, and anti-inflammatory properties, making Vernonia amygdalina a valuable resource for addressing microbial spoilage of fruits and vegetables.

Post-harvest losses due to microbial spoilage remain a critical challenge in agriculture, especially in developing countries like Nigeria. Tomatoes (Solanum lycopersicum) and peppers (Capsicum species) are staple crops in many Nigerian households and are highly perishable. They are often subject to spoilage caused by fungi such as Aspergillus spp. and bacteria like Escherichia coli and Salmonella spp. (Okpara et al., 2022). These pathogens not only reduce the quality and shelf life of produce but also pose significant health risks to consumers. The use of synthetic preservatives, while effective, has been associated with adverse health and environmental effects, prompting a shift towards natural alternatives (Chinedu et al., 2023).

The comparative efficacy of plant extracts in managing microbial contamination has been a subject of numerous studies. Both aqueous and ethanolic extracts of plants have been widely explored, with ethanolic extracts often reported to yield higher antimicrobial potency due to their ability to solubilize a broader spectrum of bioactive compounds (Eze et al., 2021). However, aqueous extracts are more readily available and cost-effective, making them an attractive option for low-resource settings.

Dutse, located in Jigawa State, Nigeria, is a key agricultural hub where tomatoes and peppers are cultivated extensively. However, the region experiences significant post-harvest losses due to microbial spoilage, exacerbated by inadequate storage facilities and high ambient temperatures. Exploring the antimicrobial potential of Vernonia amygdalina in this context is particularly relevant, as it offers a locally available, cost-effective solution to enhance the shelf life of these essential crops while mitigating health risks associated with microbial contamination (Yusuf et al., 2020).

This study focuses on comparing the antimicrobial efficacy of aqueous and ethanolic extracts of Vernonia amygdalina against fungal and bacterial isolates from spoiled tomato and pepper fruits in Dutse, Jigawa State. By identifying the more effective extract type and assessing its potential application in food preservation, the research aims to contribute to sustainable agricultural practices and food security in the region.

1.2 Statement of the Problem

Microbial contamination of food crops is a major factor contributing to food insecurity in Nigeria. Tomatoes and peppers, which are among the most widely consumed vegetables, are particularly vulnerable to spoilage caused by pathogenic microorganisms (Okpara et al., 2022). These spoilage agents not only compromise the nutritional and economic value of the crops but also pose significant public health risks due to the potential production of mycotoxins and other harmful metabolites (Eze et al., 2021).

Despite the critical role of chemical preservatives in mitigating spoilage, their usage is often limited in low-resource settings like Dutse due to cost constraints and limited awareness. Moreover, the adverse effects of synthetic preservatives on human health and the environment have necessitated the exploration of safer, natural alternatives (Chinedu et al., 2023). Plant-based extracts, particularly those derived from Vernonia amygdalina, have shown promising results in combating microbial contamination. However, the comparative efficacy of aqueous versus ethanolic extracts in this context remains poorly understood. A critical knowledge gap exists regarding the antimicrobial activity of Vernonia amygdalina extracts against specific fungal and bacterial pathogens associated with spoiled tomatoes and peppers in Dutse. Furthermore, there is limited research on the practicality and cost-effectiveness of using these extracts in real-world applications, particularly in rural communities. Addressing these gaps is essential for developing effective strategies to reduce post-harvest losses, improve food safety, and enhance the livelihoods of farmers in the region. This study seeks to bridge these gaps by evaluating the antimicrobial efficacy of aqueous and ethanolic extracts of Vernonia amygdalina against fungal and bacterial isolates from spoiled tomato and pepper fruits. The findings will not only advance our understanding of the plant's bioactive properties but also provide practical insights into its potential application in sustainable food preservation practices.

1.3 Objectives of the Study

The objectives of this study are:

1. To compare the antimicrobial efficacy of aqueous and ethanolic extracts of Vernonia amygdalina against fungal isolates from spoiled tomato and pepper fruits in Dutse, Jigawa State.

2. To evaluate the antimicrobial efficacy of aqueous and ethanolic extracts of Vernonia amygdalina against bacterial isolates from spoiled tomato and pepper fruits in Dutse, Jigawa State.

3. To identify the more effective extract type (aqueous or ethanolic) for potential application in food preservation.

1.4 Research Questions

The study will address the following research questions:

1. How effective are the aqueous and ethanolic extracts of Vernonia amygdalina against fungal isolates from spoiled tomato and pepper fruits?

2. How effective are the aqueous and ethanolic extracts of Vernonia amygdalina against bacterial isolates from spoiled tomato and pepper fruits?

3. Which type of extract (aqueous or ethanolic) demonstrates superior antimicrobial activity for potential use in food preservation?

1.5 Significance of the Study

This study is significant for several reasons. First, it contributes to the growing body of knowledge on the use of plant-based extracts as natural antimicrobial agents. By focusing on Vernonia amygdalina, a plant readily available in Nigeria, the study provides a cost-effective alternative to synthetic preservatives, which are often expensive and associated with health risks.

Second, the findings of this research will have practical applications in food preservation, particularly in rural communities like Dutse, Jigawa State, where post-harvest losses are a significant challenge. By identifying the more effective extract type, the study offers a sustainable solution to reduce microbial spoilage and enhance food security.

Lastly, this research will benefit policymakers, agricultural extension workers, and smallholder farmers by providing evidence-based recommendations for integrating natural preservatives into post-harvest management practices. It will also pave the way for further research into the use of indigenous plants for antimicrobial purposes.

1.6 Scope and Delimitation of the Study

The study focuses on comparing the antimicrobial efficacy of aqueous and ethanolic extracts of Vernonia amygdalina. The scope is limited to fungal and bacterial isolates obtained from spoiled tomato and pepper fruits collected from Dutse, Jigawa State. The microorganisms targeted include common spoilage agents such as Aspergillus spp., Escherichia coli, and Salmonella spp.

The study does not cover other plant extracts or microbial contaminants beyond the selected isolates. Additionally, the research is limited to in vitro laboratory experiments and does not extend to field trials or large-scale applications. This delimitation ensures a controlled environment for evaluating the antimicrobial properties of the extracts.

1.7 Definition of Terms

Aqueous Extract: A solution obtained by using water as a solvent to extract bioactive compounds from plant materials.

Ethanolic Extract: A solution obtained by using ethanol as a solvent to extract bioactive compounds from plant materials.

Antimicrobial Efficacy: The ability of a substance to inhibit or kill microbial organisms, including bacteria and fungi.

Post-Harvest Losses: The degradation of crops' quality and quantity after harvest, often due to microbial spoilage.

Vernonia amygdalina: A plant species commonly known as bitter leaf, widely used in traditional medicine and known for its antimicrobial properties.