(BSc Biochemistry Project)
Medicinal plants play a vital role in traditional healthcare systems and are rich sources of bioactive compounds known as phytochemicals. These phytochemicals are responsible for various biological activities, including antioxidant effects. Oxidative stress caused by free radicals has been implicated in the pathogenesis of several chronic diseases such as cancer, diabetes, cardiovascular diseases, and neurodegenerative disorders. This study investigated the phytochemical constituents and antioxidant activity of selected medicinal plant extracts using standard laboratory procedures. Fresh leaves of Vernonia amygdalina (Bitter leaf), Azadirachta indica (Neem), and Ocimum gratissimum (Scent leaf) were collected, authenticated, dried, and extracted using methanol. Qualitative phytochemical screening revealed the presence of flavonoids, tannins, saponins, phenols, alkaloids, and glycosides in varying proportions. Antioxidant activity was evaluated using the DPPH free radical scavenging assay, with ascorbic acid as the standard. The results showed significant antioxidant activity across all extracts, with Vernonia amygdalina exhibiting the highest radical scavenging potential. The study confirms that the selected medicinal plants are rich sources of natural antioxidants and supports their traditional medicinal use.
Medicinal plants have remained a cornerstone of healthcare delivery across human civilizations, particularly in developing countries where access to orthodox medicine is limited. According to the World Health Organization (WHO), about 80% of the world’s population relies on traditional medicine for primary healthcare needs. The therapeutic potential of medicinal plants is largely attributed to the presence of phytochemicals—naturally occurring chemical compounds that protect plants against environmental stress and pathogenic attacks.In recent years, there has been growing scientific interest in medicinal plants as alternative sources of antioxidants. Antioxidants are substances capable of inhibiting or delaying oxidative damage caused by free radicals. Free radicals are unstable molecules generated during normal metabolic processes or through exposure to environmental factors such as pollution, radiation, and toxins. When produced in excess, free radicals cause oxidative stress, leading to cellular damage and the development of chronic diseases.Plants synthesize a wide range of phytochemicals such as flavonoids, phenols, tannins, alkaloids, and saponins, many of which possess strong antioxidant properties. These compounds act by scavenging free radicals, chelating metal ions, and enhancing endogenous antioxidant defense mechanisms. Therefore, scientific evaluation of phytochemical composition and antioxidant activity of medicinal plants is essential for validating their traditional uses and exploring their potential in drug development.
Nigeria is richly endowed with diverse medicinal plants that are widely used in traditional medicine for treating various ailments such as malaria, infections, inflammation, diabetes, and hypertension. Despite their extensive use, many of these plants have not been adequately studied to determine their phytochemical constituents and antioxidant capacity. Synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), though effective, have been associated with toxic and carcinogenic effects, creating the need for safer, natural alternatives.Scientific investigation into plant-derived antioxidants provides a foundation for the development of safer therapeutic agents. This study therefore focuses on the phytochemical screening and antioxidant evaluation of selected medicinal plants commonly used in Nigeria.
The increasing prevalence of oxidative stress-related diseases has raised serious health concerns worldwide. While synthetic antioxidants are commonly used, their safety has been questioned due to potential adverse effects. Although medicinal plants are widely used as natural remedies, there is insufficient scientific data to support their antioxidant claims. This lack of standardized information limits their acceptance and integration into modern healthcare systems.
To evaluate the phytochemical constituents and antioxidant activity of selected medicinal plant extracts.
The findings of this study will provide scientific justification for the traditional use of the selected medicinal plants. It will contribute to the growing body of knowledge on natural antioxidants and serve as a reference for future research in biochemistry, pharmacology, and phytomedicine.
This study is limited to qualitative phytochemical screening and in vitro antioxidant activity using the DPPH method. Quantitative analysis and in vivo studies were not carried out due to time and resource constraints.
Medicinal plants are plants that possess bioactive compounds capable of preventing, alleviating, or curing diseases. They have been used since ancient times and remain relevant in modern drug discovery.
Phytochemicals are secondary metabolites produced by plants for defense and survival. Major classes include:
Alkaloids are nitrogen-containing compounds known for analgesic, antimalarial, and antimicrobial properties.
Flavonoids are polyphenolic compounds with strong antioxidant, anti-inflammatory, and anticancer activities.
Tannins possess astringent properties and play a role in wound healing and antioxidant defense.
Saponins exhibit antioxidant, cholesterol-lowering, and immune-modulating effects.
Phenols are powerful antioxidants that neutralize free radicals and prevent lipid peroxidation.
Free radicals are molecules with unpaired electrons that damage cellular components such as DNA, proteins, and lipids. Oxidative stress occurs when antioxidant defense mechanisms are overwhelmed.
Antioxidants inhibit oxidation by scavenging free radicals. Natural antioxidants from plants are preferred due to their safety and additional health benefits.
Common assays include DPPH, ABTS, FRAP, and hydrogen peroxide scavenging assays.
Traditionally used for malaria, diabetes, and gastrointestinal disorders.
Used for antimicrobial, anti-inflammatory, and antioxidant purposes.
Used in the treatment of infections, cough, and digestive disorders.
The plant samples were collected from local gardens and farms within Nigeria.
Plants were identified and authenticated by a botanist. Leaves were washed, air-dried, and ground into powder.
Maceration was carried out using methanol for 72 hours. Extracts were filtered and concentrated.
Standard qualitative tests were carried out to detect alkaloids, flavonoids, tannins, saponins, phenols, and glycosides.
The DPPH radical scavenging activity was determined spectrophotometrically at 517 nm. Percentage inhibition was calculated.
Results were expressed as mean ± standard deviation.
All plant extracts showed the presence of multiple phytochemicals. Flavonoids and phenols were abundant in all samples.
The extracts demonstrated concentration-dependent antioxidant activity. Vernonia amygdalina showed the highest DPPH scavenging activity.
The antioxidant activity observed is attributed to the presence of flavonoids and phenolic compounds, which are known free radical scavengers.
This study evaluated the phytochemical constituents and antioxidant activity of selected medicinal plants using standard biochemical methods.
The selected medicinal plants possess significant antioxidant activity and are rich in bioactive phytochemicals.
Vernonia amygdalina is widely used in Nigerian traditional medicine. In this study, it exhibited high antioxidant activity due to its rich phytochemical content, validating its traditional therapeutic use.
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