Studies on the Quantitative Evaluation of Vitamin C and Phenolic Content in Fresh Fruits and Vegetables Available in Kolkata City, West Bengal, India

Vitamin C is a water-soluble compound characterized by its acidic nature and strong reducing power [1]. Unlike most plants and animals, humans lack the ability to synthesize this vital nutrient. In natural systems, Vitamin C is predominantly found as L-ascorbic acid, while its stereoisomer, D-ascorbic acid, exhibits only about 10% of the biological activity of the L-form [2]. Structurally related to glucose, L-ascorbic acid is a weak sugar acid bound to a hydrogen ion. Under oxidative stress, it functions as a powerful reducing agent, easily transforming into its oxidized form, L-dehydroascorbic acid. This ability makes L-ascorbic acid a valuable antioxidant in the food industry, where it helps prevent oxidation-related deterioration in food products [3]. 

In humans, vitamin C plays a crucial role as a cofactor in various essential enzymatic reactions. A deficiency in this vitamin can lead to scurvy, a condition characterized by symptoms such as fatigue and bleeding gums [4]. Beyond preventing scurvy, vitamin C contributes to overall health by potentially reducing the risk of common colds, heart diseases, and enhancing the immune system. Since humans cannot produce vitamin C, it must be obtained from dietary sources [5]. Fruits and vegetables like blackcurrants, blueberries, oranges, limes, lemons, strawberries, cabbage, and malt are among the richest sources of vitamin C [6]. However, it's important to note that this vitamin is sensitive to factors such as heat and oxidation, which can lead to its degradation during cooking or processing [7]. The recommended daily intake of vitamin C for human’s ranges from 60 to 95 milligrams, with an upper intake limit set at 2000 milligrams [8]. Generally, vitamin C exhibits low acute toxicity, although long-term excessive intake may lead to issues such as diarrhea, iron overload, and kidney stones [9]. 

Ascorbic acid is considered one of the most vital vitamins present in fruits and vegetables [10]. While higher animals can synthesize L-ascorbate on their own, humans and other primates lack this ability and must obtain it through diet [11]. More than 90% of the vitamin C in the human diet is derived from fruits and vegetables, including staples like potatoes [12]. The term "vitamin C" refers to all compounds that demonstrate the biological activity of L-ascorbic acid. Although ascorbic acid is the primary active form, its oxidized counterpart, L-dehydroascorbic acid, also retains biological activity [13]. Vitamin C plays a vital role in preventing scurvy and supporting the health of skin, gums, and blood vessels [14]. It contributes to several physiological functions, including collagen synthesis, improved iron absorption, reduction of plasma cholesterol, inhibition of nitrosoamine formation, enhancement of immune function, and neutralization of singlet oxygen and other free radicals [15]. As a powerful antioxidant, vitamin C may help reduce the risk of arteriosclerosis, cardiovascular diseases, and certain types of cancer [16]. The recognized health benefits of consuming fruits and vegetables are partly due to their ascorbic acid content, which may offer protection against major health conditions [17]. This study focuses on evaluating the ascorbic acid levels in a variety of locally available fruits and vegetables [18]. 

Polyphenols are vital to human health, as they help prevent oxidative damage caused by Reactive Oxygen Species (ROS), which can lead to serious conditions like atherosclerosis, accelerated aging, and cancer [19]. The antioxidant properties of polyphenols, particularly those found in fruit peels, play a crucial role in combating these diseases [20]. Phenolic compounds and pigments are key contributors to the antioxidant activity in fruits, vegetables, cereals, and other plant-based foods [21]. As natural antioxidants, polyphenols scavenge free radicals, protecting both the plants and the human body when consumed [22]. 

Fruits generally offer more nutrients than vegetables [23]. For instance, apples (Malus domestica) from the Rosaceae family are rich in biologically active compounds, including monosaccharides, minerals, dietary fiber, and phenolics, particularly in their peels, making them a powerful source of nutrition and disease resistance [24]. Mangoes (Mangifera indica), belonging to the Anacardiaceae family, are also nutrient-dense, containing fiber, vitamins A, B, and C, as well as phenolic compounds that enhance immune function and promote overall health [25]. Additionally, the higher level of vitamin and phenolic content was found notable in cucurbits, such as bottle gourd (Lagenaria siceraria) and ridge gourd (Luffa acutangula) [26]. These gourds have been cultivated for their nutritional and medicinal properties in warm climates. Their peels, like those of apples and mangoes, are also rich in beneficial bioactive compounds [27]. 

The growing interest in substituting synthetic antioxidants with natural ones has led to increased research on the nutritional value of fruit and vegetable peels [28]. This study aims to analyze the nutritional composition and total phenolic content of various fruits [29].

Sample Preparation 

Samples for this study were sourced from a local market in Kolkata, West Bengal. Each sample was thoroughly cleaned with deionized water to eliminate any contaminants. To ensure accurate results for vitamin C, analysis was conducted on the day of purchase, addressing the compound's instability. Vitamin C content was determined following the protocols outlined in Chapter 7 of the Food Analysis Laboratory Manual, utilizing the Indophenol Method, as well as the AOAC International Methods of Analysis (Vol. 16, Method 967.21) [30]. For most samples, 100g was precisely weighed and ground with 200ml of a metaphosphoric-acetic acid solution using a mortar and pestle. This mixture was then strained through muslin, and the extract was diluted to a final volume of 1000ml with the same acid solution. 

Titrimetric Analysis 

This experiment utilizes the titration method to determine the vitamin C concentration in both freshly prepared and commercially packaged fruit juice samples. Titration, or volumetric analysis, is a common quantitative technique in laboratory settings used to measure the concentration of a specific substance. In this process, a titrant of known concentration is gradually added to a solution containing the analyte of unknown concentration. Using a calibrated burette, the volume of titrant required to reach the endpoint-indicated by a visible color change from an indicator-is precisely measured, signifying the completion of the reaction [31]. 

Estimation of Vitamin C Concentration 

For the analysis, 50ml of metaphosphoric-acetic acid solution was pipetted into each of three 500ml Erlenmeyer flasks. To each flask, 20ml of the sample extract was added. The samples were then individually titrated using 2,6-dichlorophenol indophenol blue dye until a light rose pink color remained stable for approximately 5 seconds, indicating the endpoint. The volume of dye consumed was recorded and used to calculate the vitamin C concentration [30]. In the case of fruit samples, juice was first extracted using a juice extractor, filtered, and 20ml of the resulting juice was taken for the titration process. 

Estimation of Total Phenolic Content 

The total phenolic content was determined using the Folin-Ciocalteau reagent method, as described by Malik and Singh. Diluted sample extracts of varying concentrations were transferred into 10ml glass tubes, and the total volume in each tube was adjusted to 3ml with distilled water. To each tube, 0.5ml of Folin-Ciocalteau reagent (diluted 1:1 with water) and 2ml of 20% sodium carbonate (Na₂CO₂) solution were added. This reaction led to the formation of a blue-colored complex, known as molybdenum blue, resulting from the redox interaction between phenolic compounds and phosphomolybdic acid in an alkaline medium. After briefly warming the tubes for 1 minute, they were cooled, and absorbance readings were taken at 650nm using a reagent blank as the reference. A standard calibration curve was generated using known concentrations of catechol, and the total phenol content in the test samples was calculated accordingly, expressed as milligrams of catechol equivalents per gram of sample [31].

The results of vitamin C estimation in various locally available fruits and vegetables are summarized in table 1. These findings are consistent with previous studies on vitamin C content in similar produce. Among the fruits analyzed, lemon showed the highest concentration of vitamin C, while jackfruit recorded the lowest. For vegetables, tomatoes had the highest vitamin C content, whereas green peas showed the least [32]. 

Table 1: Vitamin C content of some vegetables and fruits. 

Interestingly, some vegetables in this study exhibited lower vitamin C levels compared to values reported in other research. The data also revealed a rapid decline in ascorbic acid content for most vegetables stored at room temperature, with the exception of carrots. Notably, even under chilled conditions, a significant loss was observed in spinach and whole green peas. However, vitamin C degradation in peas, carrots, and especially broccoli was slower when stored at chill temperatures. These observations are consistent with the findings of Albrecht et al. [3], who reported high vitamin C stability in brassicas, moderate stability in peas, and poor stability in green beans. Although the hypothesis that sulfur or sulfhydryl compounds are primarily responsible for this stability was not conclusively proven [3,4], these compounds may still contribute to the retention of vitamin C. The observed loss of ascorbic acid is likely due to enzymatic oxidation. The varying rates of vitamin C degradation suggest differing susceptibilities among vegetables, influenced by factors such as surface area, mechanical damage, sulfhydryl content, and enzyme activity. Peas stored in their pods benefit from natural protection, while whole carrots and broccoli florets also retain structural integrity post-harvest [33]. In contrast, spinach leaves are particularly vulnerable to degradation after harvesting. Despite being harvested whole and with minimal physical damage, green beans appear especially prone to vitamin C loss, likely due to elevated enzymatic activity and lower sulfhydryl content. 

Given that these fruits and vegetables are both accessible and affordable in local markets; their high vitamin C content supports the recommendation to increase their consumption for meeting daily nutritional needs. This is particularly important during periods of increased physiological demand, such as pregnancy, lactation, adolescence, hyperthyroidism, infection, and post-surgical recovery. Ensuring adequate daily intake of vitamin C is crucial to prevent scurvy, a deficiency disease most commonly affecting children and the elderly [34] (Figure 1).  

 Figure 1: Vit-C concentration in different vegetables and fruits found in local bazaar, Kolkata. 

Table 2 highlights that, among the fruits studied, oranges contained the highest concentration of phenolic compounds.

Table 2: Total phenolic contents in different fruits. 

Supporting evidence from previous research indicates that the peels of Citrus grandis (pomelo) are especially rich in phenolic content [33]. This abundance of bioactive compounds in citrus fruits suggests their potential as low-cost, readily available sources of both vitamin C and phenolics, which possess strong antioxidant properties valuable in food preservation and pharmaceutical applications [34]. Moreover, the data indicate that in citrus fruits, the contribution of vitamin C surpasses that of phenolic compounds in terms of concentration. Overall, the findings suggest that citrus fruits-particularly their pulp-are excellent sources of bioactive compounds such as vitamin C and phenolics, which play important roles in scavenging free radicals and supporting overall health [35]. 

Orange (305mg/100g) has the highest phenolic content among the listed fruits. Pomegranate (294mg/100g) follows closely. These fruits are rich in antioxidants, potentially offering strong health benefits. Banana (112mg/100g) is at the lower end. While still beneficial, they contain less phenolic compounds compared to berries or guava. Phenolic compounds have antioxidant, anti-inflammatory, and antimicrobial properties [36]. Incorporating high-phenolic fruits like Musambi, pineapple, jacjfruit and Pomegranate may offer better protection against oxidative stress and related diseases [37]. Berries and dark-colored fruits (like Jamun, Black Currant, and Grapes) tend to have higher phenolic content. Tropical fruits (like Mango, Papaya, and Banana) generally show moderate to lower levels. Pomegranate (294.294mg) supports cardiovascular health. It reduces inflammation and rich in antioxidants like punicalagins and anthocyanins [38]. It may improve memory and brain function. Pineapple (190.754mg) promotes heart health and it may reduce risk of type 2 diabetes. It contains quercetin (anti-inflammatory) and good for gut microbiome. Banana (112.962mg) supports energy and heart health (potassium-rich) and aids in digestion and bowel regularity. It contains dopamine (mood enhancer). For maximum antioxidant benefits, prioritize Jamun, Guava, and Pomegranate. Mix high-phenolic fruits with lower ones for a balanced nutrient intake. There is a school of thought that darker the fruit, generally the higher the phenolic content [39,40]. 

Table 3 represents total phenolic contents in different vegetables found in Kolkata region. Phenolic compounds are plant-based antioxidants. They play a vital role in reducing oxidative stress and preventing chronic diseases. So, higher phenolic content means stronger antioxidant properties. Broccoli has highest in phenolic content and an excellent antioxidant source. Phenolic content in tomato is also high. It is commonly consumed and very beneficial for our body. Peas & Green Peas has strong antioxidant potential. Cruciferous vegetables like broccoli and cauliflower show contrasting values-broccoli is the highest, while cauliflower is mid-range. Leafy greens like spinach and cabbage have surprisingly low values, despite generally being considered nutrient-dense. Tomatoes, often underestimated for antioxidant value, are impressively high [41,42].

Table 3: Total phenolic contents in different vegetables.

The comprehensive analysis of vitamin C and phenolic content in locally available fruits and vegetables underscores their nutritional importance and antioxidant potential. Citrus fruits, particularly lemons and oranges, emerged as excellent sources of vitamin C, while vegetables like tomatoes and broccoli demonstrated notable ascorbic acid and phenolic levels, respectively. The study also highlights the variability in nutrient stability, influenced by storage conditions, structural integrity, and enzymatic activity. Spinach and green beans showed significant degradation, emphasizing the importance of proper storage and handling. Meanwhile, phenolic compounds were abundant in fruits such as pomegranate and Jamun, and vegetables like broccoli, indicating their strong antioxidant capabilities. These findings support dietary recommendations to incorporate a variety of fresh fruits and vegetables-especially citrus and cruciferous types-into daily meals to enhance antioxidant intake, support immune function, and reduce the risk of chronic diseases. Regular consumption of these affordable, locally accessible foods can play a crucial role in promoting public health, particularly for vulnerable groups with increased nutritional needs.

Authors are grateful for the permission from the Research Guidance Cell of Vivekananda College, Thakurpukur, WB. Also, I am thankful to all the graduate students for their cooperation in sample collection from different market of Kolkata for the present study.

1. Abubakar JA, Akanya HO, Garba SA (1990) A study of the ascorbic acid intake of children and aged people in selected rural suburban locations in northern Nigeria. Nigerian Journal of Science 83: 23-30.
2. Achinewhu SC (1983) Ascorbic acid content of some Nigeria local fruits and vegetables. Plant Foods for Human Nutrition 33: 261-266.
3. Albrecht JA, Schafer HW, Zottola EA (1990) Ascorbic acid retention in vegetables as affected by storage and processing methods. Journal of Food Science 55: 146-148.
4. Albrecht JA, Schaffer HW, Zottola EA (1990) Relationship of total sulphur to initial and retained ascorbic acid in selected cruciferous and non-cruciferous vegetables. Journal of Food Science 55: 181-183.
5. Albrecht JA, Zottola EA, Schaffer HW (1991) Retention of ascorbic acid in vegetables as related to sulfur and sulfhydryl compounds. Journal of Food Science 56: 1057-1059.
6. Albrecht A, Schaffer HW, Zottola EA (1991) Sulphydryl and ascorbic acid relationships in selected vege- tables and fruits. Journal of Food Science 56: 427-430.
7. Association of Official Analytical Chemists AOAC (1995) Official Methods of Analysis, Association of Official Analytical Chemists, Washington, D.C, USA.
8. Balasundram N, Sundram K, Samman S (2006) Phenolic compounds in plants and agri-industrial by-products: Antioxidant activity, occurrence, and potential uses. Food Chemistry 99: 191-203.
9. Ball GFM (2006) Vitamins in Foods: Analysis, Bioavailability, and Stability. CRC Press.
10. Carr AC, Frei B (1999) Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. The American Journal of Clinical Nutrition 69: 1086-1107.
11. Cartea ME, Francisco M, Soengas P, Velasco P (2011) Phenolic compounds in Brassica vegetables. Molecules 16: 251-280.
12. Chatterjee S, Variyar PS (2015) Bioactive components in banana and their associated health benefits-A review. Food Reviews International 31: 1-22.
13. Davey MW, Montagu MV, Inzé D, Sanmartin M, Kanellis A, et al. (2000) Plant L-ascorbic acid: Chemistry, function, metabolism, bioavailability and effects of processing. Journal of the Science of Food and Agriculture 80: 825-860.
14. Davidson S, Passmore R, Brocks JA (1972) Human Nutrition and Dieterics. Churchill, Livingstone, London, UK.
15. Eheart MS, Odland D (1972) Effect on ascorbic acid, sugars, and total acids: Storage of fresh broccoli and green beans. Journal of the American Dietetic Association 60: 402-406.
16. Faria A, Calhau C (2011) The bioactivity of pomegranate: Impact on health and disease. Critical Reviews in Food Science and Nutrition 51: 626-634.
17. Food and Nutrition Board, Institute of Medicine (2000) Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academies Press.
18. Huang D, Ou B, Prior RL (2005) The chemistry behind antioxidant capacity assays. Journal of Agricultural and Food Chemistry 53: 1841-1856.
19. Ignat I, Volf I, Popa VI (2011) A critical review of methods for characterisation of polyphenolic compounds in fruits and vegetables. Food Chemistry 126: 1821-1835.
20. Kaur C, Kapoor HC (2001) Antioxidants in fruits and vegetables–the millennium’s health. International Journal of Food Science & Technology 36: 703-725.
21. Lee SK, Kader AA (2000) Preharvest and postharvest factors influencing vitamin C content of horticultural crops. Postharvest Biology and Technology 20: 207-220.
22. Levine M, Rumsey SC, Wang Y, Park JB, Daruwala R (1999) Vitamin C. In Handbook of Antioxidants. CRC Press.
23. Luthria DL, Pastor-Corrales MA (2006) Phenolic acids content of fifteen dry edible bean (Phaseolus vulgaris) varieties. Journal of Food Composition and Analysis 19: 205-211.
24. Mahapatra AK, Mishra S, Basak UC, Panda PC (2012) Nutrient analysis of some selected edible fruits of deciduous forests of India: An explorative study towards nonconventional bio-nutrient. Adv J Food Sci Technol 4: 15-21.
25. Malik CP, Singh MB (1980) Plant Enzymology and Histo-Enzymology. Kalyani Publishers, India.
26. Manach C, Scalbert A, Morand C, Rémésy C, Jiménez L (2004) Polyphenols: Food sources and bioavailability. The American Journal of Clinical Nutrition 79: 727-747.
27. Nagata M, Yamashita I (1992) Simple method for simultaneous determination of chlorophyll and carotenoids in tomato fruit. J Japan Soc Food Sci Technol 39: 925-928.
28. Naidu KA (2003) Vitamin C in human health and disease is still a mystery? An overview. Nutrition Journal 2: 7.
29. Nielsen SS (2010) Food Analysis Laboratory Manual. Springer, Berlin, Germany.
30. Ninfali P, Bacchiocca M (2003) Polyphenols and antioxidant capacity of vegetables under fresh and frozen conditions. Journal of Agricultural and Food Chemistry 51: 2222-2226.
31. Pandey KB, Rizvi SI (2009) Plant polyphenols as dietary antioxidants in human health and disease. Oxidative Medicine and Cellular Longevity 2: 270-278.
32. Pereira DM, Valentão P, Pereira JA, Andrade PB (2009) Phenolics: From chemistry to biology. Molecules 14: 2202-2211.
33. Podsedek A (2007) Natural antioxidants and antioxidant capacity of Brassica vegetables: A review. LWT - Food Science and Technology 40: 1-11.
34. Ranganna S (1986) Handbook of Analysis and Quality Control for Fruit and Vegetable Products. Tata McGraw-Hill, USA.
35. Rice-Evans CA, Miller NJ, Paganga G (1997) Antioxidant properties of phenolic compounds. Trends in Plant Science 2: 152-159.
36. Siddiq M, Sogi DS, Dolan KD (2013) Fruit and Vegetable Peels: Their Composition and Potential Uses. In: Fruit and Vegetable Waste: Bioactive Compounds, Their Extraction, and Use.
37. Singleton VL, Orthofer R, Lamuela-Raventós RM (1999) Analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. Methods in Enzymology 299: 152-178.
38. Skoog DA, West DM, Holler FJ, Crouch SR (2014) Fundamentals of Analytical Chemistry. Brooks/Cole.
39. Rekha C, Poornima G, Manasa M, Abhipsa V, Devi JP, et al. (2012) Ascorbic acid, total phenol content and antioxidant activity of fresh juices of four ripe and unripe citrus fruits. Chem Sci Trans 1: 303-310.
40. Vinson JA, Hao Y, Su X, Zubik L (1998) Phenol antioxidant quantity and quality in foods: Vegetables. Journal of Agricultural and Food Chemistry 46: 3630-3634.
41. Vuong QV, Hirun S, Chuen TLK, Goldsmith CD, Bowyer MC, et al. (2014) Phenolic compounds and antioxidant properties of peel extracts from Citrus species. Journal of Agricultural and Food Chemistry 62: 6821-6830.
42. WHO/FAO (2004) Vitamin and Mineral Requirements in Human Nutrition. World Health Organization and Food and Agriculture Organization of the United Nations.