by CHAPTER ONE
INTRODUCTION
Background of the Study
The increasing prevalence of antimicrobial resistance and oxidative stress-related diseases has intensified the global search for effective natural alternatives to synthetic drugs and preservatives. Medicinal plants have emerged as a valuable source of bioactive compounds with therapeutic potential, particularly due to their antimicrobial and antioxidant properties. Among these, scent leaf (Ocimum gratissimum) and hibiscus leaf (Hibiscus sabdariffa) have gained attention for their rich phytochemical profiles and traditional uses in ethnomedicine (Akinmoladun et al., 2017). The field of antibacterial research is of utmost importance in the fight against infectious diseases. With the rise of antibiotic resistance, there is a growing need to explore alternative sources of antibacterial agents. One such source is plant extracts, which have been used in traditional medicine for centuries. Plants have been found to be a major source of medicine and humans have relied on them over the years. In present days, most people in developing countries continue to rely on plants as a primary form of medicine. This is due to antimicrobial resistance of microorganisms which has become a major global problem and a threat to the successful treatment of infectious diseases. Plants have proven to be a potential solution to this problem. They are fortified with defense mechanisms which they use to fight against pathogenic and harmful microbes and prevent them from causing serious damage. A few antimicrobial drugs have been obtained from numerous plant species so far, and some of these include Quinine (antimalarial) from Cinchona ledgerian, the antimalarial compound Artemisin, derived from Artemisia annua, ginseng which has been observed to have antibacterial activity against Escherichae coli and Staphylococcus.
Scent leaf, commonly used in West African cuisines and herbal remedies, is known for its potent antimicrobial, anti-inflammatory, and antioxidant effects, primarily due to the presence of compounds such as eugenol, thymol, flavonoids, and phenolics (Ilori et al., 2016). Hibiscus leaf, on the other hand, contains anthocyanins, polyphenols, and organic acids, which contribute to its antioxidant and antimicrobial activity (Da-Costa-Rocha et al., 2014). These properties make both plants promising candidates for developing natural antimicrobial and antioxidant agents. The effectiveness of plant-derived extracts, however, is significantly influenced by the type of solvent used during extraction. Solvents differ in polarity, which affects their ability to solubilize different groups of phytochemicals. For instance, polar solvents like ethanol and methanol are generally more effective in extracting phenolic compounds, while non-polar solvents such as hexane target lipid-soluble components (Tiwari et al., 2011). Understanding how different solvents impact the yield and bioactivity of plant extracts is essential for optimizing their medicinal applications. The leaves of the plant are rich in bioactive compounds such as phenols, flavonoids, alkaloids, and essential oils, which contribute to its therapeutic potential.6 The antimicrobial activity of scent leaf has been a subject of interest in scientific research. Gabriel (2021) investigated its efficacy against various bacterial strains. For instance, research has shown that scent leaf extracts exhibit antibacterial activity against pathogens such as Escherichia coli, Staphylococcus aureus, Salmonella typhi, and Pseudomonas aeruginosa. Scent leaf extracts have been studied for their antifungal properties. They have demonstrated inhibitory effects against fungi like Candida albicans, which is responsible for causing oral thrush and other fungal infections. This antifungal activity further highlights the therapeutic potential of scent leaf in combating microbial infections. Apart from its antimicrobial properties, scent leaf has also been investigated for its antioxidant and anti-inflammatory effects. The presence of bioactive compounds in the plant contributes to its antioxidant activity, which helps neutralize harmful free radicals in the body. Additionally, scent leaf extracts have exhibited antiinflammatory activity in various experimental models, suggesting its potential use in managing inflammatory conditions from various species of microorganisms that suppress the growth of other microorganisms and eventually may destroy them. The probable points of difference amongst the antibiotics may be physical, chemical, pharmacological properties, antibacterial spectra, and mechanism of action. They have made it possible to cure diseases caused by bacteria, such as pneumonia, tuberculosis, and meningitis, and they save the lives of millions of people around the world. Antibiotics are important to treat infections and have saved countless lives. However, anytime antibiotics are used, they can cause side effects and contribute to antibiotic resistance, one of the most urgent threats to public health. Antibiotics are used to treat or prevent some types of bacterial infection. They work by killing bacteria or preventing them from reproducing and spreading. (Atkinao, 2020)
Ciprofloxacin is an antibiotic agent in the fluoroquinolone class used to treat bacterial infections. It exerts its effect by binding to and inhibiting bacterial DNA-gyrase. This enzyme produces supercoiling of cellular DNA which is needed for bacterial DNA synthesis. It has an in vitro activity against many gramnegative and gram-positive organisms. Ciprofloxacin is indicated for treatment of several bacterial infections, including bacterial bronchitis, pneumonia, sinusitis, urinary tract infections, septicemia, joint and bone infections, soft tissue and skin infections, typhoid fever, anthrax, bacterial gastroenteritis, urethral and gynecological infections, bacterial conjunctivitis, pelvic inflammatory disease and several other infectious conditions. (Mathins, 2019) The emergence of resistant bacterial strains against the commonly prescribed antibiotics in hospitals is a worldwide problem. Most ocular bacterial infections are primarily treated with broad spectrum antibiotics. However, widespread and misuse of these antibiotics for bacterial and viral infections or prophylactics has resulted in emerging global increase of antibiotic resistance. Antibiotic resistance for ocular bacteria has also been observed to be caused by factors such as empirical prescribing of antibiotics, short-term exposure to antibiotics, and repeated exposure to the same antibiotic identified as contributing to resistance of ocular pathogens, as well as leading to changes in resident ocular flora. Most often, people stick to self-medication and empirical treatments with broad spectrum antibiotics and these contribute to antibiotic resistance. Diagnosis of most external ocular infections are given without proper laboratory culture and confirmation. In this case, these infections are treated empirically, with a failure to take into account the possibility of multidrug resistant bacteria, such as Methicillin resistant Staphlyococcus aureus being a problem
Statement of the Problem
The increasing resistance of microorganisms to conventional antimicrobial agents and the growing health concerns associated with synthetic antioxidants have intensified the search for natural alternatives. Medicinal plants such as Ocimum gratissimum (scent leaf) and Hibiscus sabdariffa (hibiscus leaf) have shown considerable antimicrobial and antioxidant potential due to their rich phytochemical contents. However, the effectiveness of these bioactivities largely depends on the method of extraction, particularly the type of solvent used.
Despite numerous studies on the medicinal properties of these plants, there is limited information on how different solvent extraction methods influence their antimicrobial and antioxidant capacities. Solvent polarity plays a critical role in the type and quantity of phytochemicals extracted, which in turn affects the biological activity of the extracts. Without a clear understanding of the most effective extraction conditions, the full therapeutic potential of these plants may not be realized or optimized for industrial or pharmaceutical use.
