Investigation Of Total Phenolic And Flavonoid Content Present In The Leaf And Stalk Extracts Of Ocimum Gratissimum (Scent Leaf) Cultivated In Jos, Nigeria.

Investigation of Total Phenolic and Flavonoid Content Present in the Leaf and Stalk Extracts of Ocimum Gratissimum (Scent Leaf) Cultivated In Jos, Nigeria

¹Chukuka Achuenu, ²Emesi Ijeoma Chinenye, ³Raymond Dashe, ³Edah Alexander O, *⁴Suleman Stephen M

¹Department of Chemistry, University of Jos, PMB 2084, Jos, Nigeria

²National Biotechnology and Development Agency (NABDA), Abuja, Nigeria

³Department of Pharmaceutical and Medicinal Chemistry University of Jos, PMB 2084, Jos, Nigeria

⁴Department of Chemistry Nigerian Army University Biu PMB 1500, Biu, Borno State, Nigeria

DOI: https://doi.org/10.51244/IJRSI.2025.12010049

Received: 29 December 2024; Accepted: 06 January 2025; Published: 12 February 2025

ABSTRACT

The present study examines the total phenolic and flavonoid content in the leaf and stalk of Ocimum gratissimum grown in Jos by using the maceration method for extraction. Ethanol and ethyl acetate were used as solvents for the extraction of bioactive compounds from the plant material. Total phenolic content (TPC) of the extracts was determined as Gallic Acid Equivalent (GAE). The results showed that the TPC of the ethyl acetate extract was significantly higher (231.78 ± 2.3609 mg/100g GAE) than that obtained from ethanol extract (182.61 ± 0.7765 mg/100g GAE). Ethyl acetate, hence, proved to be a better solvent in extracting phenolic compounds from this plant material. The study also determined the total flavonoid content (TFC) of the extracts. The results revealed that the ethanol extract gave a higher TFC for the stalk (345.23 ± 1.80 mg/100g GAE) compared to the ethyl acetate extract, while the ethyl acetate extract had a higher TFC for the leaf (124.86 ± 2.44 mg/100g GAE). These differences establish that both solvent type and plant part affect the efficiency of flavonoid extraction. The results generally reveal that O. gratissimum grown in Jos contained considerable amounts of phenolic and flavonoid compounds, comparable to those cultivated in other parts of the world. The study also highlighted the fact that the solvent employed played an important role in optimizing the extraction of the bioactive compounds. Ethyl acetate is more efficient at extracting phenolic, whereas ethanol is more effective for flavonoids in specific plant parts. This adds valuable information about the phytochemical profile of Ocimum gratissimum, which has pointed out its potential applications in pharmaceuticals and nutraceuticals.

Keywords: Extracts, Analyses, Phytochemicals, Cyclopentanepropanoic, Maceration.

MATERIALS AND METHODS

Introduction

Plants are among the most valuable sources of drugs in both traditional and modern medicine, as well as in the production of nutraceuticals, food supplements, pharmaceutical intermediates, and chemical entities for synthetic drugs (Hammer et al., 1999). The use of plants and their derivatives for medicinal purposes dates back to the dawn of human civilization. Medicinal plants play a crucial role in the health of individuals and communities, with their therapeutic properties attributed to certain chemical compounds that have specific physiological effects on the human body. Key bioactive compounds in these plants include alkaloids, tannins, flavonoids, and phenolic compounds. Many traditional medicinal plants also serve as spices and food sources (Okwu, 2001).

Ocimum gratissimum, a member of the Lamiaceae family native to tropical Africa, is renowned for its extensive medicinal properties and is widely distributed across the globe. The essential oils derived from its leaves are rich in various bioactive compounds, particularly phenolic compounds, which are known for their antioxidant, anti-inflammatory, and anticancer properties (Saha et al., 2013; Prabhu & Rajan, 2015). Assessing the total phenolic content of these essential oils is vital for evaluating their potential health benefits and therapeutic uses (Kumari et al., 2017).

As an ethnobotanical plant, Ocimum gratissimum represents a significant source of natural drugs for research and development (Kong et al., 2008). Plant-based medicinal drugs are advantageous due to their simplicity, effectiveness, and broad-spectrum activity. The World Health Organization (WHO) and many developing countries have renewed their interest in African medicinal plants, leading to increased efforts to document ethnomedical knowledge, which is traditionally passed down orally by healers. Researchers are increasingly focusing on natural products to discover new drug leads for treating cancer, as well as viral and microbial infections. Phytochemical analysis of Ocimum gratissimum reveals its richness in alkaloids, tannins, phytates, flavonoids, and oligosaccharides (Ijeh et al., 2004). In Nigeria’s coastal regions, this plant is traditionally used to treat epilepsy, high fever, and diarrhea (Sofowara, 1993; Ladipo et al., 2010).

Ocimum gratissimum, widely recognized for its medicinal and nutritional value, is a perennial plant prevalent in the tropics of Africa and Asia. It belongs to the Labiatae family and is the most abundant species of the Ocimum genus. Commonly known as the Basil Fever plant or Tea bush, it has various vernacular names, including ‘Daidoya tagida’ in Hausa, ‘Nichonwu’ in Igbo, ‘Tanmotswangiwawagi’ in Nupe, and ‘Efinrin’ in Yoruba (Abdullahi et al., 2003; Okigbo & Igwe, 2007).

This woody-based plant typically grows to a height of 1-3 meters, with broad, narrowly ovate leaves measuring 5-13 cm in length and 3-9 cm in width. It is a fragrant shrub with lime-green leaves (USDA, 2008). Among the Igbo people, the plant is consumed as a leafy vegetable and is valued for its nutritional importance, particularly as a seasoning due to its aromatic flavor. It is also used in Igbo culture to manage the baby’s umbilical cord, believed to help keep the cord and surrounding area sterile (Ebi & Ofoefule, 1997).

Plant Material and Extraction

The fresh leaf and stalk of Ocimum gratissimum was purchased from ‘Faringada’ Market in Jos metropolis, Plateau State, Nigeria. The plant materials were rinsed with distilled water to remove sand particles and was air dried at room temperature for 7 days. The dried plant material was separated into leaf and stalk and was crushed separately with mortar and pestle into coarse powder. Two portions of 50 g each of powdered Ocimum gratissimum leaf and stalk was macerated using 250 ml of ethanol and 250 ml of ethyl acetate for 72 hours respectively with periodic shaking. The solution was then filtered using Whatman No. 1 filter paper to obtain the filtrate. The filtrate was evaporated using water bath at 40 ^OC. The percentage yield of leaf and stalk in ethanol extract and ethyl acetate extract was calculated as 19.2 % and 20.6 % ,19.0 % and 16.6 % respectively.

Determination of Total Phenolic Content of the leaf extracts

Total phenolic content (TPC) of the extracts ethanol and ethyl acetate were measured using colorimetric method following the Folin-Ciocalteu method reported by Akinseye., et al (2017), with slight modification where 100 mg of the extract of the sample was weighed accurately and dissolved in 100 ml of distilled water. 1.5 mL of this solution was transferred into a test tube, then 1 mL 2 N of the Folin-Ciocalteu reagent and 2 mL 20% of Na₂CO₃ solution was added and ultimately the volume was made up to 8 mL with distilled water followed by shaking and finally allowed to stand for 2 hours after which the absorbance was taken at 710 nm. These data were used to estimate the total phenolic content using a standard calibration curve obtained from various diluted concentrations of gallic acid standard curve (20-100 µmL). The modification for the estimation of TPC was based on the Folin-Ciocalteu method but with a difference in the preparation of the sample. This means that 100 mg of the extract was dissolved in 100 mL of distilled water. In the assay, 1.5 mL of the solution is used. Probably, sample preparation in the original method might not have been similar to this. This adjustment is aimed at ensuring the results are reproducible: A standard concentration of the extract solution, which is 100 mg in 100 mL, will yield consistent, repeatable results and optimizing the reagent interaction. The solution is used instead of weighing the extract directly into each assay tube and hence easier to handle and ensures uniform mixing and absorbance readings. This modification allows adaptation of the method to the characteristics of the sample and laboratory setup without compromising the reliability of the method.

Determination of Total Flavonoid Content

The total flavonoid content was determined using the method of Ordonez et al (2006). A volume of 0.5ml of 2% of Alcl3 ethanol solution was added to 0.5ml of extract solution. The mixture was incubated for 1hr at room temperature for yellow color appearance; the absorbance was measured at 420 nm.  Plant extracts were evaluated at final concentration of 0.1mgml-1. Total flavonoids content was calculated as quercetin equivalent (mg/g) using the equation obtains from the curve:

RESULTS AND DISCUSSION

Total phenolic content of the ethanol and ethyl acetate extracts of the leaf were obtained using a standard method. The absorbance of the sample mixture and the reagent (blank) were measured with colorimeter at 710 nm as shown in table 1. Then the amount of total phenol in 1 g of the extract was calculated with the use of gallic acid as standard for the calibration curve as shown in fig 1. Table 2 and Fig. 2 indicate that ethyl acetate extracts exhibited a higher TPC of 231.78 ± 2.3609 mg/100g GAE more than that of ethanol extract of 182.61± 0.7765 mg/100g GAE. This indicates that ethyl acetate is more efficient than ethanol in extracting phenolic compounds from

Ocimum gratissimum leaf. The total flavonoid contents of the ethyl acetate extract of the leave and stalk were obtained using standard method. The absorbance of the sample mixture and the reagent were measured with colorimeter at 420 nm. Then the amount of the total flavonoid in 1 g of ethanol was calculated with the use of Gallic acid as standard for the calibration curve. The analysis confirms higher percentage Total Flavonoids content (TFC) in the stalk than the leaf, while ethanol provided higher percentage of TFC in the stalk, ethyl acetate provided higher in the leaf as shown in table 3. Fig. 3 shows that the ethanol extracts of the stalk and ethyl acetate of the stalk has higher flavonoid content. This variation may be attributed to the selective solubility of phenolics and flavonoids in different solvents, emphasizing the solvent’s critical role in phytochemical extraction. The results corroborate the work of Saha et al. (2013), who noted the influence of solvent polarity on the extraction of bioactive compounds in Ocimum gratissimum. Ethanol’s superior performance in extracting flavonoids from the stalk aligns with observations in similar studies on medicinal plants (Okwu, 2001). The phytochemical richness observed in Ocimum gratissimum in this study is consistent with findings by Hammer et al. (1999), who reported high levels of bioactive compounds in Lamiaceae family members. Additionally, the study’s conclusion that both solvent type and plant part affect the efficiency of compound extraction is supported by the work of Kong et al. (2008), which emphasized the structural variation of plant tissues influencing bioactive compound solubility.

Table 1: Gallic Acid Standard for Total Phenolic Content

Fig. 1. Gallic Acid Standard Curve

Table 2: Result of Total Phenolic Content of Leaf Extract

Fig. 2. Bar Chart of Total Phenolic Content of Leaf Extract

Table 3. Total flavonoid of leaf and stalk extracts

Fig. 3. Total Flavonoid (mg/100g of Extract in QE)

CONCLUSION

In conclusion, this study demonstrates that Ocimum gratissimum leaf and stalk contain significant amounts of phenolic contents and flavonoids, with ethyl acetate being a more efficient solvent for extracting phenolic compounds than ethanol. The above claim is as a result of the higher total phenolic content observed in the ethyl acetate extract (231.78 ± 2.3609 mg/100g GAE) compared to the ethanol extract (182.61±0.7765 mg/100g GAE). The higher percentage Total Flavonoids Content (TFC) in the stalk than the leaf was obtained. The ethanol extract provided higher percentage of TFC in the stalk than that of the ethyl acetate, while on the other hand, ethyl acetate provided higher percentage Total Flavonoids Content in the leaf than the ethanol extract. Further studies should be conducted to investigate the bioactivity of the extracted phenolic and Flavonoids compounds to determine their potential health benefits and applications in pharmaceuticals or nutraceuticals. The use of other solvents or solvent combinations should be explored to further enhance the extraction efficiency.

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