Effect of net shading and season on plant growth, productivity and quality of bush tea (Athrixia phylicoides DC.)

Bush tea (Athrixia phylicoides DC.) is a South African native plant that grows naturally in different parts of South Africa that are characterized by different climatic conditions. The effects of agricultural practices on plant growth, yield and chemical composition of bush tea have been studied on pots experiment under controlled environment. However, the effect of shade net and season on field grown bush tea and its quality have not yet investigated. Hence, its quality is determined by the accumulation, partitioning and distribution of secondary metabolites which are affected by major abiotic and biotic factors which include environmental conditions, UV light, temperature, water availability, type and composition of soil. Currently, there is no recommended best production method and season for bush tea crop in Southern Africa that maximizes plant growth, yield, accumulation, partitioning and distribution of secondary metabolites. Therefore, this thesis evaluated the effect of the application of shade nets and season on plant growth, development and quality of bush tea. Net shade application reduced bush tea plant growth and yield when compared to plants exposed to direct sunlight during the summer season. Hydroxycinnamic acid recorded higher in 80% white shade net plots than the plants exposed to direct sunlight. The study also evaluated the effect of UV-induced geometrical isomerization of hydroxyl-cinnamic acid-containing molecules of bush tea using ultra high-performance liquid chromatogram quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS). The study highlighted that light impacted the chemistry of plants which results in the formation of newly formed metabolites which are not naturally part of the plant. Secondary metabolites which have been responded to photo isomerization were discovered to be structurally related by the formation of a very tight molecular family using when molecular networking algorithm. This study also investigated the metabolite diversification of bush tea through glucaric acid conjugation by cinnamic acid derivatives using UHPLC-QTOF-MS. The findings revealed that hydroxyl-cinnamic acids (HCAs) derivatives undergo photo-isomerization during post ultra-violet (UV) light exposure, evidenced by the emergence of photo-isomers. The study indicated the ability of conducive environment to promote plant growth, development, yield as well as enhancing quality of bush tea. Future prospects will include investigation of the effect of different colours of ultraviolet light on bush tea extracts and response of molecular network of bush tea exposed to different types of shade nets using UHPLC-QTOF-MS.Agriculture and  Animal HealthD. Phil. (Agriculture

Eco-physiological response of secondary metabolites of teas: Review of quality attributes of herbal tea

Herbal tea is a rich source of secondary metabolites which are reputed to have medicinal and nutritional efficacy. These secondary metabolites are influenced by the abiotic and biotic stresses that improve the production of herbal teas in terms of biomass production, accumulation and partitioning of assimilates of compounds. In this study, various examples of herbal teas have been shown to respond differently to secondary metabolites affected by environmental factors. Thus, the meta-analysis of this study confirms that different herbal teas' response to environmental factors depends on the type of species, cultivar, and the degree of shade that the plant is exposed. It is also evident that the metabolic processes are also known to optimize the production of secondary metabolites which can thus be achieved by manipulating agronomic practices on herbal teas. The different phenolic compound in herbal teas possesses the antioxidant, antimicrobial, antiatherosclerosis, anti-inflammatory, antimutagenic, antitumor, antidiabetic and antiviral activities that are important in managing chronic diseases associated with lifestyle. It can be precluded that more studies should be conducted to establish interactive responses of biotic and abiotic environmental factors on quality attributes of herbal teas

Performance of selected different types of stone fruits in a summer rainfall area, South Africa

M.Sc.(Agric)Department of Horticultural Science

Metabolite Profile of Athrixia phylicoides DC. (Bush Tea) and Determination of Inhibitory Mechanism against Tyrosinase Enzyme from Mushroom

Athrixia phylicoides DC. (Bush tea) is a shrub harvested in the north-eastern mountain regions of South Africa and belongs to the Asteraceae family. Generally, A. phylicoides is consumed as a hot tea beverage for its associated health benefits. The use of bush tea extracts for beauty enhancement has not been investigated even though several ethnobotanical reports have indicated its usage against skin imperfections. Therefore, the aim of the study was to assess plant metabolites of A. phylicoides for their inhibition of tyrosinase from mushroom and determine their inhibitory mechanism. Methanolic extracts (80% v/v) of A. phylicoides were evaluated using a tyrosinase-based TLC (thin-layer chromatography) autography technique. The inhibitory mechanism of active metabolites against the enzyme was determined using Lineweaver–Burk plots. Quercetin and an unknown metabolite with a retention factor (Rf) value of 0.73 inhibited melanogenesis. However, the IC50 value for Quercetin was reported as 51.07 ± 2.43 µg/mL higher than that of kojic acid of 5.22 ± 1.44 µg/mL. Chlorogenic acid was reported to have a similar Rf value as kojic acid, suggesting similarities in polarity and affinity towards the adsorbent material. However, chlorogenic acid with an IC50 value of 15.25 ± 1.18 µg/mL and an inhibitory strength of 2.92 could not inhibit melanogenesis with a similar intensity as kojic acid. The inhibitory mechanism for A. phylicoides extract was reported to be mixed inhibition (competitive/uncompetitive). The IC50 value for A. phylicoides was recorded as 20.65 ± 0.14 µg/mL with an inhibitory strength of 3.96. These results suggest that A. phylicoides extracts could be used against dark spots associated with scarring and ageing through modulation of tyrosinase activity

Metabolite Profile of <i>Athrixia phylicoides</i> DC. (Bush Tea) and Determination of Inhibitory Mechanism against Tyrosinase Enzyme from Mushroom

Athrixia phylicoides DC. (Bush tea) is a shrub harvested in the north-eastern mountain regions of South Africa and belongs to the Asteraceae family. Generally, A. phylicoides is consumed as a hot tea beverage for its associated health benefits. The use of bush tea extracts for beauty enhancement has not been investigated even though several ethnobotanical reports have indicated its usage against skin imperfections. Therefore, the aim of the study was to assess plant metabolites of A. phylicoides for their inhibition of tyrosinase from mushroom and determine their inhibitory mechanism. Methanolic extracts (80% v/v) of A. phylicoides were evaluated using a tyrosinase-based TLC (thin-layer chromatography) autography technique. The inhibitory mechanism of active metabolites against the enzyme was determined using Lineweaver–Burk plots. Quercetin and an unknown metabolite with a retention factor (Rf) value of 0.73 inhibited melanogenesis. However, the IC50 value for Quercetin was reported as 51.07 ± 2.43 µg/mL higher than that of kojic acid of 5.22 ± 1.44 µg/mL. Chlorogenic acid was reported to have a similar Rf value as kojic acid, suggesting similarities in polarity and affinity towards the adsorbent material. However, chlorogenic acid with an IC50 value of 15.25 ± 1.18 µg/mL and an inhibitory strength of 2.92 could not inhibit melanogenesis with a similar intensity as kojic acid. The inhibitory mechanism for A. phylicoides extract was reported to be mixed inhibition (competitive/uncompetitive). The IC50 value for A. phylicoides was recorded as 20.65 ± 0.14 µg/mL with an inhibitory strength of 3.96. These results suggest that A. phylicoides extracts could be used against dark spots associated with scarring and ageing through modulation of tyrosinase activity

Response to various water regimes of the physiological aspects, nutritional water productivity, and phytochemical composition of bush tea (Athrixia phylicoides DC.) grown under a protected environment

The influence of water regimes on plants is crucial for integrating bush tea (Athrixia phylicoides DC.) into strategies in Sub-Saharan Africa to tackle food and nutritional insecurity by considering physiological aspects, nutritional yield, nutritional water productivity, and metabolite composition. The objective of the study was to determine the physiological aspects, including leaf gas exchange and chlorophyll fluorescence, nutritional yield, nutritional water productivity, and metabolite composition of bush tea under varying water regimes. The tunnel experiment was laid out in a randomized complete block design (RCBD) with treatments consisting of three water regimes: 100% of crop water requirement (ETa), 30% of ETa, and a control (no irrigation), all replicated three times. The morphological aspects were recorded on a weekly basis. However, yield, nutrient content, nutritional water productivity (NWP), and phytochemical composition were determined at harvest. The phytochemical analysis by liquid chromatography mass spectrometry (LC-MS), coupled with visualization of the detected chemical spaces through molecular networking, indicated Athrixia phylicoides DC. to be rich in various bioactive compound derivatives, including methyl chlorogenate, flavonoids, tartaric acid, caffeoylquinic acid, and glutinane. The results showed that 30% ETa enhanced plant growth, nutrient content, and nutritional water productivity compared to other water treatments. Nevertheless, 100% ETa yielded more (95.62 kg ha−1) than 30% ETa (60.61 kg ha−1) and control (12.12 kg ha−1). The accumulation of chlorogenic acids was higher under 30% ETa compared to 100% ETa and control. Therefore, this study is the first to determine the accumulation of various bioactive compounds in bush tea leaf extracts under varying water regimes. This confirms that in areas with low water availability, bush tea is well adapted for production without limiting nutrients