Effect of Solvent Type on Total Phenolic Content and Free Radical Scavenging Activity of Black Tea and Herbal Infusions

Abstract

The objective of the study was to determine and compare the effect of several solvents namely hot water, 50 % methanol, ethanol, 50 % ethanol, acetone, 50 % acetone and ethyl acetate on phenolic composition and free radical scavenging activity in black tea and selected herbal infusions from Zimbabwe and Brazil. For the black tea, made from Camellia sinensis, Quickbrew™ was used. Zimbabwean herbal infusions used were Lippia javanica and Ficus sycamore while those from Brazil were Syzygium j a m b o l a n u m , C u p h e a c a r t h a g e n e n s i s a n d I l e x paraguariensis. Total phenolic content and free radical scavenging activity were determined using Folin-Ciocalteu and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay, respectively. IC 50 values for each solvent were calculated and used to interpret radical scavenging activity. Aqueous organic solvents extracted higher quantities of phenolic compounds than in their absolute organic nature. Acetone (50 %) extracted a higher total phenolic content (TPC) in C. sinensis, L. javanica and I. paraguariensis. Hot water extracted the highest TPC in F. sycamore and S. jambolanum while 50 % ethanol was highest in C. carthagenensis. Free radical scavenging activity (FRSA) was not necessarily in the same order as TPC, indicating that high TPC does not always mean high FRSA and vice versa. The highest FRSA for S. jambolanum and C. carthagenensis extracts was in 50 % ethanol, F. sycamore in 50 % methanol, and I. paraguariensis, C. sinensis and L. javanica extracts in 50 % acetone. Ethyl acetate recorded the lowest TPC and FRSA in all plant samples analysed. Generally, solvent used affected TPC and free radical scavenging activity. Organic solvents may need to be separated from phenolics after extraction, as some of them namely acetone, methanol and ethyl acetate can be toxic to humans. Water and ethanol are the least toxic solvents which may need no further separation from extracts.

New Pharmacophore from the Stem Bark Fractions of Acacia decurrens (Willd), an Invasive South Africa Tree

“…This result implies that most of the secondary metabolites are hydrophilic in nature and consistent with the literature report which confirms methanol as the most suitable solvent for extraction of the polar secondary metabolite [25]. There has been a report that polarity significantly affects the recovery yields of the secondary metabolites from the plant [26].…”

Lippia javanica (Burm.f.) Spreng.: Traditional and Commercial Uses and Phytochemical and Pharmacological Significance in the African and Indian Subcontinent

“…According to Shikanga et al [7], L. javanica tea is appreciated throughout its distributional range as a general health tonic and also because it is naturally caffeine-free and has a calming and relaxing effect. Research done by other workers, for example, Manenzhe et al [2], Shikanga et al [7], Parrant [8], Olivier et al [81], Motlhanka and Makhabu [9], and Bhebhe et al [10, 11], revealed that L. javanica is a popular recreational tea in southern Africa, consumed on a daily basis within a food context, while medicinal infusions or tisanes of L. javanica are taken for a specific medical purpose. During the past 20 years, the use of herbal teas has increased globally [107] because of their functional properties and consumer interest in the health promoting properties of such beverages [108].…”

“…Bhebhe et al [10] determined the total phenolic and tannin content and radical scavenging activities of L. javanica , comparing it with Aspalathus linearis (Burm.f.) R. Dahlgren (Rooibos™), a commercial South African herbal tea, and other popular herbal teas in Zimbabwe (Table 3).…”

“…The tannin content of L. javanica is very low when compared to A. linearis (Rooibos) (Table 3). Lippia javanica has higher radical scavenging activity than A. linearis (Table 3) which is probably due to higher total phenolic content in comparison to A. linearis which is a popular herbal tea consumed by 10% of the global herbal tea market [10]. In another study, Bhebhe et al [11] determined and compared the effect of several solvents, namely, hot water, 50% methanol, ethanol, 50% ethanol, acetone, 50% acetone, and ethyl acetate, on phenolic composition and free radical scavenging activity in common black tea, C. sinensis, and five other well-known herbal teas including L. javanica .…”

“…Shikanga et al [7] found leaf extracts of L. javanica to have higher phenolic content of 14.8 mg/g gallic acid equivalent of dry weight than flowers (9.9 mg/g) and twigs (8.3 mg/g). Phenolic compounds found in plants are known to play an important role as antioxidants in exhibiting the medicinal properties such as antibiotic, anti-inflammatory, anticancer, and antiallergic properties [10, 66, 130, 131]. …”