Nutritional, Phytochemical, Antioxidant and Genetic characterization of Jackfruits (Artocarpus Heterophyllus) found in selected regions of Kenya and Uganda

Abstract

Some sections of the work included in the thesis have been published in peer reviewed journals and they include Chapter three ‘(European Journal of Medicinal Plants)’ and chapter four ‘(Journal of Advances in Biology and Biotechnology).’ Additionally, Chapter four has been accepted with corrections in Journal of Crop Improvement. According to Food and Agriculture Organization (FAO) of the United Nations, 821 million people were affected by food and nutrition insecurity in 2017 worldwide of which 3.4 million people were in Kenya. This was attributed to overdependence on a few food crops for nutritional needs. Therefore, there is need to find alternative sources of nutrition in Kenya to minimize food and nutrition insecurity. Jackfruit is an underutilized plant and it is a potential alternative nutritional source in Kenya. However, no study has been conducted to determine the nutritional, phytochemical, antioxidant and genetic characterization of Jackfruit in Kenya. This study sought to (i) Determine the nutritional profile, phytochemical content, and antioxidant activities of jackfruit seeds and pulp in selected regions of Kenya and Uganda. (ii) Compare the phytochemical content and antioxidant activities of jackfruit roots, leaves and bark, found in selected regions of Kenya and Uganda and (iii) Compare the effectiveness of various pre-treatment protocols for seed germination and DNA extraction from leaves, and (iv) determine the genetic diversity of jackfruits from selected sites in Kenya and Uganda. The nutritional analysis was conducted using fresh weight, whereas mineral analysis was conducted using dry weight. The moisture contents in the pulp and seeds were (62.67-70.42%) and (44.76-50.54%) respectively. The ash, lipid, protein and carbohydrate content values were all higher in the seeds than in the pulp. The values were: seeds (1.12 -1.64%) and pulp (0.34 -0.48%) for ash content, seeds (0.41-0.50%) and pulp (0.09-0.12%) for lipid content, seeds (14.11 to 16.26%) and pulp (10.56 to 13.67%) for protein content and seeds (31.41%-34.95%) and (21.65 to 24.91%) pulp for carbohydrate content. Both jackfruit seeds and pulp were rich in essential minerals such as potassium, sodium, calcium, magnesium, zinc and iron. Phytochemical analysis revealed that the phenolic and flavonoid contents, as well as DPPH scavenging activity, and the reducing power values were higher in the seeds than in the pulps. Moreover, the roots had the highest phenolic, flavonoids and tannin content, while the bark had the least. The phenolic contents were roots (67.37- 59.00 mg/g) and bark (30.88 - 16.30 mg/g). Similarly, the flavonoids compositions were roots (10.74 - 7.31 mg/g) and bark (3.09 – 1.49 mg/g). The tannin contents were roots (3.88 - 2.69 mg/g), and bark (0.93 -0.52 mg/g). Notably, the DPPH scavenging activity was also highest in the roots (66 -72%), while that of the bark was the least (24 - 40%). The reducing power of the roots, leaves and bark were from (114.38 – 93.62 μg/ml), (71.63-67.04 μg/ml) and (54.16-33.15 μg/ml) respectively. In genetic characterization, the initially sampled young leaves from mature trees, yielded degraded DNA, which is attributable to high concentration of phytochemicals in the leaves. A resampling of the fruits was done and the seeds germinated using an optimal protocol. The fresh seeds that were pre-soaked in 3% hydrogen peroxide took the shortest time to germinate compared to those that were pre-soaked in 3% hydrochloric acid and distilled water. The seeds pre-soaked in 3% sulphuric acid did not germinate. The extraction of DNA from leaves obtained from the seedlings was also unsuccessful using five different protocols. Subsequently, modification of one of the techniques resulted in high yield and good quality DNA. The optimised CTAB protocol had additional steps of phenol chloroform (1:1 w/v), chloroform isoamyl alcohol (24:1) and chloroform, which ensure complete removal of secondary metabolites. Additionally, it did not employ liquid nitrogen and beta-mercaptoethanol; hence, it is suitable for research labs in low resource settings. Jackfruit samples from different regions were characterized using Simple sequence repeats (SSR) and Sequence-related amplified polymorphism (SRAP) markers. The average values for the polymorphic SSR markers were gene diversity (0.55), PIC (0.48), Simpson’s diversity index (0.48) and observed heterozygosity (0.42). The average of the genetic diversity parameters using polymorphic SRAP markers were gene diversity (0.61), PIC (0.56), Simpson’s diversity Index (0.61) and observed heterozygosity (0.47). The PCoA analysis for the combined SSR and SRAP markers revealed that most samples from the same region, were closely related and the correlation coefficient of their genetic diversity parameters was 0.78. Jackfruit was found to have moderate genetic diversity and all parts of the tree studied were beneficial. The pulp and seeds are potential good alternative sources of nutrition, while the roots, barks, leaves, seeds and pulp can be used as natural antioxidants sources