Antioxidant Activity, Total Phenolic and Flavonoids Contents of Roma Tomatoes (Peel and Pulp) Obtained from Gboko, Benue State, Nigeria.

Hassan B. Y. et al., Antioxidant Activity, Total Phenolic……. 120 Nigerian Journal of Pharmaceutical and Biomedical Research Vol. 8 Issue.2 August, 2024. p-ISSN: 2579-1419 e-ISSN: 2814-1423 Antioxidant Activity, Total Phenolic and Flavonoids Contents of Roma Tomatoes (Peel and Pulp) Obtained from Gboko, Benue State, Nigeria. Hassan B. Yesufu* Rofiat F. Adewunmi2 Falmata M. Aliyu1, Nafiu A. Lawan1 1Department of Pharmaceutical Chemistry, University of Maiduguri, Borno State 2Department of Biochemistry, Baba Ahmed University, Kano, Kano State Corresponding author address; y[email protected], Orchid No. 0000-0003-4351-7707 DOI No.: http://doi.org.10.55639/607.phar.101201.0015 Abstract Tomatoes are a staple fruit in Nigeria, cherished for their culinary versatility, particularly the Roma tomato, which is predominantly sold in the Maiduguri market and sourced from Gboko, Benue State. Rich in antioxidants such as lycopene, lutein, and beta-carotene, tomatoes offer significant health benefits, including protection against light-induced damage to the eyes, cataract development, and age-related macular degeneration (AMD). This study investigates the antioxidant properties of Roma tomatoes by separating the samples into pulp and peels, which were then air-dried and extracted using ethanol and n-hexane solvents through a maceration method. The total phenolic content and antioxidant composition were assessed using standard protocols. Results revealed that the ethanol extract of Gboko pulp exhibited the highest antioxidant activity at 96.02%. The peel extracts showed high (ETH peel-81.93) to moderate (NH-peel-63.14) antioxidant levels, while Gboko NH pulp (0.69) recorded the least concentration at the various concentrations (0.5 mg/ml, 0.25 mg/ml, and 0.125 mg/ml). The n-hexane extract (Pulp) showed higher phenolic content (1.707) and higher flavonoid content (2.095) for the peels indicating its potential as a functional food with health-promoting properties. These findings underscore the nutritional value of tomatoes, particularly the Roma variety, emphasizing their role in promoting eye health and overall well-being in Nigerian diets. Introduction A large number of epidemiological and clinical studies have shown that a high antioxidant dietary intake is associated with lower incidence of cardiovascular diseases (Zhishen et al., 1999), atherosclerosis, arthritis, cancer (Giovannucci, 1999) and aging. Phenolic and flavonoids compounds such as quercetin, resveratrol, curcumin, rutin, catechins etc. which are present naturally in vegetables, fruits, grains and pulses, possess the ability to reduce oxidative damages (Lee, et al., 2001). Tomatoes are rich in vitamins, minerals, and phytochemicals, particularly phenolic compounds and flavonoids, which are known for their antioxidant properties. The antioxidant activity is essential in combating oxidative stress, which is linked to various chronic diseases, including cancer and cardiovascular disorders (Adefegha and Oboh, 2019). Solanum lycopercicum L., popularly called Roma tomatoes belong to the Solanaceae family along with potatoes, eggplants and tobacco (Imran et al., 2020). It is a widespread vegetable crop known for its Hassan B. Y. et al., Antioxidant Activity, Total Phenolic……. 121 pleasant taste, color, high nutritive content, and diversified use as a basic ingredient in a large variety of raw, cooked or processed foods. In addition to these properties, tomato seeds are a source of fiber. The vitamins commonly found in Roma tomato are vitamin C, A and E, which benefits the immune system, promotes the absorption of minerals (such as iron and calcium) and necessary for proper blood coagulation (Ali et al., 2021). Tomatoes (Solanum lycopersicum) are not only a staple in culinary applications but also a significant source of bioactive compounds known for their health benefits. Roma tomatoes, in particular, are prized for their rich flavor and nutritional profile (Gorecka et al., 2020). This study focuses on assessing the antioxidant activity, total phenolic, and flavonoid contents of Roma tomatoes, specifically analyzing both the peel and pulp obtained from Gboko, Benue State, Nigeria. The increasing interest in natural antioxidants due to their potential health benefits underscores the significance of such research. 2.0 Materials and Methods 2.1 Materials All the chemicals and reagents used are of analytical grade. Ethanol, Ethyl acetate, Methanol Hexane, Ascorbic acid (Vitamin C), Folin ciocalteu reagent, Gallic acid monohydrate, Lead acetate, Fehling’s solution A and B were purchased from Central Drug House (CDH) India. 2.2 Extract preparation Fresh tomatoes (Gboko) were bought from Maiduguri Monday market, Borno state, Nigeria. The tomatoes were sliced into two and the peels as well as the pulps were separated from the seeds. The separated parts were shade dried, pulverized to moderately coarse powder and weighed. 4.16 g and 3.53 g aliquots of the peel and the pulp were extracted with 200mL of 80% Ethanol and nHexane using reflux method and concentrated using a rotary evaporator. 2.3 Phytochemical Screening 2.3.1 Test for Flavonoids and Phenolic Hydroxyl Group 2.3.1.1 Ferric chloride test The extracts (0.5g) was dissolved in distilled water and then filtered. To the filtrate (2mL) a few drops of 10% ferric chloride solution are then added. The appearance of a green blue violet coloration is an indication of the presence of phenolic hydroxyl group (Trease and Evans, 2002) 2.3.1.2. Sodium hydroxide test The extract (0.5g) was dissolved in distilled water and filtered. To the filtrate, 10% of aqueous sodium hydroxide (2mL) was added to produce a yellow color. A change in color from yellow to colorless on addition of dilute HCL is an indication of presence of flavonoids (Shahidi and Zhong, 2005). 2.4. Total Phenolic Content The phenolic compounds estimation was conducted using Folin-Ciocalteu colorimetric method (Singleton et al., 1999; Song et al., 2010). 40 µL plant extract was measured into a test tube, 3.16mL distilled water and 200µL Folin-Ciocalteu reagent was added and mixed. After 8 minutes, 600 µL sodium carbonate solutions (20%) was added, mixed and incubated at 400C centigrade for 30 minutes. The blank Hassan B. Y. et al., Antioxidant Activity, Total Phenolic……. 122 contained Methanol in place of sample. The absorbance was measured at 765nm. The total phenolic content was expressed as µg/ml of Gallic Acid Equivalent (GAE). 2.5 Total Flavonoids Content The estimation of flavonoids content was carried using Aluminum Colorimetric method by (Sahreen et al., 2010). 300µL plant extract was measured into a test tube, 3.14mL of 30% aqueous methanol was added. To the same solution, 150µL of 0.5M sodium nitrite, 150µL of 0.3M Aluminum chloride and 1mL of 1M NaOH was added within 5 minutes intervals after each addition. The absorbance was measured at 506nm. Control contained methanol in place of sample. The total flavonoids content was expressed in µg/mL of Ascorbic Acid Equivalent (AAE). 2.6 In-Vitro Antioxidant Assay 2.6.1. DPPH radical scavenging activity assay The free radical scavenging activity of the extracts was measured in vitro by 2, 2′- diphenyl-1-picrylhydrazyl (DPPH) assay according to the method described earlier (Yesufu et al. 2018). The stock solution was prepared by dissolving 24 mg DPPH with 100 mL methanol and stored at 20°C until required. A 3 mL aliquot of this solution was mixed with 100 μL of the sample at various concentrations (0.125mg/mL – 1.0 μg/ml). The reaction mixture was shaken well and incubated in the dark for 35 min at room temperature. Then the absorbance was taken at 517 nm. The control was prepared as above without any sample. The scavenging activity was estimated based on the percentage of DPPH radical scavenged as the following equation: Scavenging effect % = Control absorbancesample absorbance Control absorbance × 100 3.0 Results Table 1: Qualitative Analysis of phenolic and flavonoids content in Roma Tomatoes Hassan B. Y. et al., Antioxidant Activity, Total Phenolic……. 123 Sample Phenolic compounds Flavonoids ETH Peel + + NH Peel + + ETH Pulp + + NH Pulp + + Key: ETH-Ethanol NH: n-Hexane +: Positive Table 2: Quantitative Analysis of the Phenolic and Flavonoids contents of Roma Tomatoes Plant Material Phenolic content (mg/g) Flavonoids content (mg/g) ETH Peel 0.772 2.088 NH Peel 1.054 2.095 ETH Pulp 1.593 1.95 NH Pulp 1.707 1.95 Key: ETH-Ethanol, NH: n-Hexane Figure 1: Antioxidant activities of different Concentrations of Roma Tomato Peel and Pulp extracts 0 20 40 60 80 100 VIT C Gboko Peel Eth Gboko Peel NH Gboko Pulp Eth Gboko Pulp NH Radical Scavenging Potential of Roma tomato Cultivars 0 0.125 0.25 0.5 1 Hassan B. Y. et al., Antioxidant Activity, Total Phenolic……. 124 (a) (b) IC50 = 7.75 IC50 = 3.23 (c) (d) IC50 = 4.07 IC50 = 1.63 (e) IC50 = 1.56 Figure 2: IC50 of different Solvent extracts of Roma Tomato Peel and Pulp 4.0 Discussion Roma tomatoes are consumed worldwide as vegetables due to their high contents of essential nutrients and antioxidant-rich phytochemicals commonly known as secondary metabolites (Kumar et al., 2021; Iswari and Susanti, 2016). The results in table 1 and 2 shows the qualitative and quantitative analysis of phenolic and flavonoids contents in Gboko Roma Tomatoes. The results revealed higher values of total phenolic in the pulp and high flavonoids contents in the peel, the non-polar n-hexane extract seemed to have greater portion of the phenolic and y = 8.645x - 17.065 R² = 0.5132 -20 -10 0 10 20 30 40 50 0246 Gb NH Pulp y = 10.293x + 16.711 R² = 0.3655 0 20 40 60 80 0 2 4 6 Gb NH Peel y = 16.315x - 16.412 R² = 0.939 -20 0 20 40 60 80 0123456 Gb ETH Peel y = 18.387x + 10.904 R² = 0.5901 0 20 40 60 80 100 120 0 2 4 6 Gb ETH Pulp y = 19.55x + 19.37 R² = 0.5022 0 50 100 150 0123456 A.A Hassan B. Y. et al., Antioxidant Activity, Total Phenolic……. 125 flavonoid content. Which perhaps suggest their lipophilic nature. Several studies have revealed that tomatoes are highly rich in flavonoids and phenolic contents and compound such Quercetin, Carotenoids, Kaempferol, Naringenin and Lutein and Dihydrochalcone phloretin 3', 5'-di-C-betaglucopyranoside among others have been isolated from tomatoes. Bianchi et al. (2023) reported that Tomatoes contained, primarily conjugates of quercetin and kaempferol, which have been identified as phenolic compounds. The result of the antioxidant activity of different concentrations of Roma tomatoes peel and pulp as presented in Figure 1 revealed significant antioxidant activities as shown by the different concentration of the extracts; however, the pulp extract exhibited the best activity when compared to the peels, this may be due to synergy attributed to the presence of other compounds such as Vitamin C, Vitamin E and carotenoids that might be in abundant in pulp compared to peel. The findings therefore disagree with the report by Pérez-Jiménez et al.( 2010), that the peel of Roma tomatoes possesses higher total phenolic content. However, it agrees with statement on the flavonoid contents. The antioxidant activity, as evidenced by the DPPH assay, further supports the assertion that tomato pulp are a valuable source of natural antioxidants. The high phenolic and flavonoid levels correlate with the observed antioxidant capacity, suggesting that incorporating tomato pulp in diets could provide additional health benefits. According to Merenkova et al., 2020, the combination of vitamins, minerals, carotenoids, vitamin C, vitamin E, and phenolic compounds confers tomatoes antioxidant activities thereby neutralizing reactive oxygen species (ROS) and protecting the cell membrane against lipid peroxidation, which protects the human body against various oxidative stress-related diseases, such as cancer, cardiovascular diseases, cognitive function and osteoporosis (Fuentes, et al., 2021) The study highlights the significant antioxidant activity and rich content of total phenolic and flavonoid compounds in Roma tomatoes, particularly in the pulp. 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