Browsing by Author "Mapa, S. T."

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Comparison of total chlorophyll, carotene and phenolic contents between species/varieties of Sri Lankan green leafy vegetables Sesbania grandiflora, Centella asiatica and Ipomea aquatica
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Dahanayaka, L. W.; Kadigamuwa, C. C.; Mapa, S. T.
Green Leafy Vegetables (GLVs) are rich sources of phytochemicals which are beneficial to reduce chronic non-communicable diseases due to their therapeutic properties such as antioxidant activity. Among numerous dietary supplements of phytochemicals, GLVs are under spotlight as they are rich sources of phenolics and natural pigments including chlorophylls and carotenoids. Availability and the amount of these phytochemicals may vary depending on many factors including the variety of GLVs. The aim of this study is to quantitatively analyze the phytochemical contents; total phenol, chlorophyll and carotene among 3 selected GLV species and 2 varieties of each, Sesbania grandiflora, Centella asiatica and Ipomea aquatica. Each home garden grow variety was acquired from same geographical location which have similar growth conditions. Edible parts of each sample were well washed, air dried at room temperature under shade, and oven dried at 45 ºC to obtain a constant weight. Dried samples were ground and tests were carried out using homogenous sample powder. Total chlorophyll and carotene contents were determined by measuring the absorbance (at the wavelengths of 470 nm, 645 nm and 662 nm) of methanolic extracts and using formulas. Total chlorophyll content in leafy vegetables ranged from 13.75 to 35.56 μg/g dry weight of the sample. The highest chlorophyll content was observed in S. grandiflora variety 1 (V1), whereas the lowest chlorophyll content was observed in I. aquatica variety 2 (V2). The carotene content of studied leaf samples was within the range of 1.08 to 3.89 mg/g dry weight of the sample. S. grandiflora V1 had the highest carotene content whereas the lowest carotene content was observed in C. asiatica V1. Total Phenolic Content (TPC) was determined by the Folin-Ciocalteu method by measuring the absorbance at 760 nm using the methanolic extracts of leaf samples. TPC were within the range of 3.62 to 18.19 mg GAE/g dry weight of the sample. S. grandiflora V1, leaves showed the highest TPC as 18.19 mg GAE/g dry weight of the sample and the lowest TPC was observed in C. asiatica V2 as 3.62 mg GAE/g dry weight of the sample. The results were analyzed in one-way analysis of variance ANOVA test, which showed a statistically significant difference between species/varieties (p
A preliminary study to investigate the impact of geographical variation on phytochemical content and antioxidant properties of selected green leafy vegetables
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Dahanayaka, L. W.; Kadigamuwa, C. C.; Mapa, S. T.
Green leafy vegetables (GLVs) are rich sources of phytochemicals with significant therapeutic potentials including antioxidant activity, mitigating non-communicable diseases. The phytochemicals and antioxidant properties may vary depending on many factors including geographical location. This preliminary study aimed to analyze the variation of these properties in two selected GLV species; Ipomea aquatica and Alternanthera sessilis with geographical location. Plant samples were acquired from different geographical locations (low-country dry zone – Jaffna, up-country intermediate zone – Welimada/Ella, low-country wet zone – Kalutara/Hikkaduwa) cultivated under organic farming practices. A pot study (with controlled growth conditions) was carried out at Gampaha (low-country wet zone). Edible plant parts were cleaned, oven-dried at 45 ºC, ground, and the methanolic extracts were prepared. Each experiment was carried out in triplicates. The total flavonoid content (TFC) and the total phenolic content (TPC) were determined by the aluminium chloride colorimetric assay and Folin-Ciocalteu method respectively. 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and ferric ion-reducing antioxidant power (FRAP) assay were used to determine the antioxidant activity. For statistical analysis, the one-way analysis of variance (ANOVA) test which indicates significant differences among locations, and Tukey’s post hoc test to identify statistically significant differences between locations (p < 0.05) were carried out. A. sessilis showed significant differences towards all experimented aspects (chlorophyll, carotene, TFC, and FRAP) except TPC and DPPH. I. aquatica showed significant differences in chlorophyll and TFC. However, several locations were not significantly different in some aspects. TPC in A. sessilis from Jaffna and Ella were not significantly different from Hikkaduwa, while DPPH of Hikkaduwa and Gampaha were not different from Jaffna. The carotene content of I. aquatica did not show any significant difference between Kalutara and Gampaha samples. The TPC of I. aquatica was not significantly different in the samples of Jaffna, Welimada, and Gampaha. The difference in DPPH inhibition was not significant in Jaffna and Gampaha, while FRAP was not significantly different between Kalutara and Jaffna as well as Welimada and Gampaha. The results indicate that geographical location has contributed to the variation of some experimented aspects. Furthermore, the highest TFC for both plants was recorded from Jaffna samples, while the highest DPPH activity was recorded with the high-altitude locations (Ella and Welimada). No such pattern was observed with other variables. These results evidence the possible variations in the phytochemical composition and antioxidant activity of GLVs depending on the geographical location. This knowledge can be used to establish comprehensive research to investigate the correlation of geographical variations with phytochemical and antioxidant properties, guide agricultural practices, select better cultivation sites, improve the quality of herbal medicines, and enhance the nutritional value of GLVs.