Anti-inflammatory and anti-oxidant activities of ethanolic extracts of Tamarindus indica L. (Fabaceae)

Abstract

Various parts of Tamarindus indica L are used to treat inflammatory disorders. This study evaluated the anti-inflammatory and antioxidant activities of the ethanolic extracts of the root and stem bark of the plant. The carrageenan-induced paw edema model of inflammation in chicks was used to assess anti-inflammatory activity. The phosphomolybdenum (PM) assay, 2, 2—diphenyl—1—picrylhydrazyl (DPPH) radical and hydrogen peroxide scavenging assays were used to investigate antioxidant potential. Total phenolic content was evaluated by the Folin–Ciocalteu method. Both stem bark and root extracts possessed similar total phenolic content (11–13 g/100 g AAE) and had comparable total antioxidant capacities (about 27 g/100 g GAE). However, the stem bark extract was a better scavenger of both DPPH radicals and hydrogen peroxide, with lower IC₅₀ values than the root extract. In the anti-inflammation test, both extracts exhibited dose-dependent reduction of edema, similar to the standard drugs used. The root extract, with ED₅₀ of 118.1 ± 1.9 mg/kg, proved superior to the stem bark extract, whose ED₅₀ was 154.5 ± 2.6 mg/kg. The results showed that both stem bark and root extracts possess potent anti-inflammatory and anti-oxidant activity and confirm their use in folkloric medicine.

Keywords:

• herbal plant validation
• carrageenan-induced paw edema
• total antioxidant capacity
• phosphomolybdenum assay
• inflammation

PUBLIC INTEREST STATEMENT

Tamarindus indica L, (tamarind) is a common plant in West Africa and parts of Asia. Known as yooyi in Ga (a Ghanaian language), the different parts of the plant are used for various purposes in traditional herbal medicine. The seeds are used in the treatment of chronic diarrhea and dysentery. The roots and bark are used as remedies for treating ulcers, boils, rashes, eye and skin inflammation, indigestion and to promote wound healing. The leaves and flowers of the plant are also used to treat swollen joints, boils and sprains. This research work was undertaken to provide a scientific validation for the use of the plant in herbal medicine. The results of the study show that ethanol extracts of the root and stem bark of the plant are very good in reducing inflammation and neutralizing free radicals.

1. Introduction

Tamarindus indica L., also known as tamarind, is a member of the Fabaceae family and belongs to the subfamily Caesalpinioideae. The plant is a hardwood tree and is a very important tree in many tropical countries. The plant is found mainly in Africa and Asia, but is said to be indigenous to tropical West Africa where the main belt runs from, Sierra Leone, Liberia, Ivory Coast and Ghana, all through to the equatorial regions of Cameroun, the Republic of Congo and Kenya (El-Siddig, 2006). The plant is commonly referred to as “Saamia” in Hausa and “Yooyi” in Ga. It is also sometimes referred to as “date of India”. The tamarind tree produces bean-like pods, filled with seeds and surrounded by a fibrous pulp as fruit. The fruit pulp possesses a sweet acidic taste that is attributed to the presence of high amounts of reducing sugars and tartaric acid. The importance of Tamarindus indica L. is highlighted by the fact that almost every part of the plant has some use in the pharmaceutical, food, chemical and textile industries (Bhadoriya et al., 2011; Havinga et al., 2010). Reports indicate that commercial plantations dedicated to the plant exist in some Central American states as well as Brazil (Sharma & Bhardwaj, 1997). The fruit pulp is used to flavor confections, curries and sauces, as a seasoning in prepared foods, and as a major ingredient in juices and other beverages (Bhadoriya et al., 2011).

In traditional medicine, the seeds of tamarind are used in the treatment of chronic diarrhea and dysentery. The roots and bark are used as remedies for treating ulcers, boils, rashes, eye and skin inflammation, indigestion and to promote wound healing. The leaves and flowers of the plant are also used to treat swollen joints, boils and sprains (Bhadoriya et al., 2011; Havinga et al., 2010). The plant is known for its anti-inflammatory (Komakech et al., 2019; Sundaram et al., 2015), antihelminthic (Das et al., 2011), antioxidant (Reis et al., 2016), hepato-protective (Amir et al., 2016; Rodriguez Amado et al., 2016), cytotoxic (Al-Fatimi et al., 2007), antimicrobial (Doughari, 2006), analgesic (Gupta & Singh, 2017; Komakech et al., 2019), antiasthmatic (Tayade et al., 2009), hypolipidaemic and weight-reducing (Jindal et al., 2011) activities. Investigations into the constituents of the plant have revealed the presence of phytochemicals such as alkaloids, sesquiterpenes, saponins, tannins, flavonoids and phlobatamins (Abukakar et al., 2008; Doughari, 2006). Phenolic compounds such as catechin, epicatechin and procyanidin B have been shown to be present in the plant (Rasul et al., 1989). Two triterpenes, lupanone and lupeol were isolated from the leaves of Tamarindus indica (Imam et al., 2007). The anti-inflammatory potential of lupeol has been widely investigated (Fernández et al., 2001; Geetha & Varalakshmi, 2001; Saleem, 2009; Zhu et al., 2016).

Inflammation is a pathophysiological response and defense mechanism that helps the body to protect itself against infection, burn, toxic chemicals, allergens or other noxious stimuli. Inflammation is normally associated with pain, redness, irritation and swelling. When the inflammatory pathway is triggered, inflammatory mediators such as bradykinin, prostaglandins and histamine are released. These chemical substances cause narrow blood vessels to expand. As a result, blood flow easily to the affected area leading to redness and hotness of the area. Prostaglandins produced as a result of inflammation cause pain at the affected area. An uncontrolled and persistent inflammation may result in many chronic illnesses and the mediators involved in the inflammation process can induce, maintain or aggravate many diseases (Eming et al., 2007; Koh & DiPietro, 2011; Vane & Botting, 1987). Inflammation thus can lead to uncomfortable situations. There are many drugs available to help with inflammation conditions. Drugs that are currently used for the management of inflammation conditions are steroidal anti-inflammatory drugs and non-steroidal anti-inflammation drugs (NSAIDs). NSAIDs remain the mainstay of therapy to treat a wide variety of inflammatory diseases. These drugs do not cure the disease but rather modify the inflammatory response to the disease. The use of NSAIDs is often limited by gastrointestinal side effects, ranging from dyspepsia to bleeding from ulceration which can be life-threatening. It has been reported that NSAIDs inhibit the cyclooxygenase (COX) pathway and as such interfere with the synthesis of the agents responsible for sustaining gastric mucosal integrity—prostaglandins (Rainsford, 1999). Therefore, the need to develop newer and safer anti-inflammatory drugs still exists.

In general, medicines derived from plants are perceived to be safer than their synthetic equivalents (Shaw et al., 2012). Herbal medicine remains the most common go-to treatment method for approximately 70% of the world’s population due to its effectiveness and perceived minimal side effects. The World Health Organization (WHO) recognizes herbal medicine as an essential cog in primary health care for many countries. The heavy dependence on folkloric treatment in many developing countries is due to the cost of pharmaceutical remedies and the uneasy access to health care delivery (World Health Organization, 2005). Since Tamarindus indica L is one of the plants widely used in Ghana in the management of inflammation-associated ailments, the current study was designed to evaluate the anti-inflammatory activities of the ethanolic bark and root extracts of the plant. Furthermore, the strong association between factors that cause oxidative damage (such as reactive oxygen and nitrogen species, free radicals) and inflammation (Mangge et al., 2014) prompted an evaluation of the antioxidant activities of the extracts.

We herein report on the anti-inflammatory and antioxidant activities of the ethanolic extracts of the stem bark and root of Tamarindus indica L. Results of the study show that both extracts possess promising anti-inflammatory properties with both extracts reducing inflammation in a dose-dependent manner. Both extracts also showed promising radical scavenging potential and antioxidant capabilities.

2. Methods

2.1. Collection of plant materials and extraction

Plant materials used for this study were collected in September 2018 from Kwahu in the Eastern Region of Ghana. Both root and stem bark samples were collected. Plant identification and authentication were done by Mr. Clifford Asare, a botanist at the Department of Herbal Medicine, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi—Ghana. Specimens of the sample collected were deposited at the Pharmacy herbarium. Drying of plant samples was carried out at room temperature, away from sunlight, for 14 days. When the weight of samples became constant, samples were milled and used for extraction. The dried, pulverized plant sample was then extracted via the Soxhlet method. Ethanol (99%) was used as the solvent in a ratio of 1:5 (plant material: solvent). The extract obtained was then concentrated under reduced pressure with a rotary evaporator (Cole Parmer, N-1110, China). The concentrated extracts were transferred into a petri dish, dried at room temperature and stored in a refrigerator until use.

2.2. Anti-inflammatory assay

2.2.1. Animals

The day-old chicks (Gallus gallus) used for this study were obtained from Akate Farms in Kumasi, Ghana. The chicks were kept at Animal House of the Department of Pharmacology, KNUST where they were acclimatized for 7 days. During this time, feed was available ad libitum. The chicks were kept within a 12-h light-dark cycle. After 7 days, the chicks were weighed and placed into groups, with 15 chicks per cage. Each treatment group consisted of 5 animals. The Guidelines for the Care and Use of Laboratory Animals by the National Institute of Health were used throughout this work.

2.2.2. Carrageenan-induced paw edema assay

Anti-inflammatory activity of the extracts was assessed in chicks with the carrageenan-induced paw edema model of inflammation. Extracts and standard drugs were prepared in normal saline. The initial volume of the left foot of the chicks was obtained with a digital Vernier caliper and used as the baseline. To induce inflammation, 0.1 mL of 1% carrageenan was injected sub—plantar into the left foot of the chicks. Ninety (90) min post–carrageenan administration, animals received varying concentrations of extracts (30, 100 and 300 mg/kg). Positive control treatment groups received either standard diclofenac (10, 30 and 100 mg/kg) or standard dexamethasone (0.3, 1 and 3 mg/kg). Normal saline was administered to the negative control treatment group. Foot volumes were measured 90 min post–carrageenan injection, 30 min after extract or drug administration and every hour thereafter till the 4^th hour (Roach & Sufka, 2003; Borquaye et al., 2017).

2.2.3. Data analysis

The raw scores for each foot volume were normalized as the percentage difference from the initial foot volume, then averaged for each treatment group. Change in foot volume was computed with Equation (1)(1) $\mathrm{\%}Changeinfootvolume=\frac{Footvolumeattime,t-Footvolumeattime,t=0}{Footvolumeattime,t=0}X100$(1) ;

(1) $\mathrm{\%}Changeinfootvolume=\frac{Footvolumeattime,t-Footvolumeattime,t=0}{Footvolumeattime,t=0}X100$(1)

The area under the curve (AUC), presented in arbitrary units, was used to express the total foot volume for each treatment group. Equation (2)(2) $\mathrm{\%}Inhibitionofedema=\frac{AUCcontrol-AUCtreatment}{AUCcontrol}X100$(2) was then used to estimate the percentage inhibition of edema for each treatment group:

(2) $\mathrm{\%}Inhibitionofedema=\frac{AUCcontrol-AUCtreatment}{AUCcontrol}X100$(2)

To analyze differences in AUCs for control or each treatment, one-way analysis of variance (ANOVA) followed by Dunnett’s post hoc test was used. The dose responsible for 50% of maximal effect (ED₅₀) for each extract or standard drug, was determined using an iterative computer least square method (Borquaye et al., 2017). GraphPad Prism Version 6.0 (GraphPad Software, San Diego, CA, USA) was used for all statistical analyses and ED₅₀ calculations.

2.3. Total phenolic content (Folin–Ciocalteu method)

A test tube was filled with 5 mL of 10% Folin-Ciocalteu reagent. To this, 1 mL of sample solution or standard drug (gallic acid) was then added. The mix was shaken and allowed to sit for 5 min at room temperature. After this, 7% NaHCO3 (4 mL) was added slowly. The reaction mixture was then incubated away from light at room temperature for 30 min. Absorbance readings were taken at 765 nm (Perkin Elmer Lambda 35). The phenolic content was expressed as gallic acid equivalent (GAE) (Gyesi et al., 2019).

2.4. Antioxidant assays

2.4.1. Hydrogen peroxide scavenging assay

The method of Gyesi and coworkers was used. Gallic acid was used as the standard drug. To 0.5 mL of 1 mM ferrous ammonium sulphate and 125 µL of 5 mM H₂O₂ was added 3 mL of different concentrations of extracts or gallic acid. The mixture was incubated at room temperature for 5 min in the dark. Thereafter, 3 mL of 1,10-phenanthroline (1 mM) was added to each reaction mixture, mixed thoroughly and incubated again for 10 min at room temperature. Absorbance was taken at 510 nm (Perkin Elmer Lambda 35 UV-Vis spectrophotometer). Water was used in place of extract for the blank solution. There were 3 replicates for each concentration. The percentage of hydrogen peroxide scavenged was obtained using Equation (3)(3) $\mathrm{\%}HydrogenPeroxideScavenged=\frac{Atest}{Acontrol}X100$(3) ;

(3) $\mathrm{\%}HydrogenPeroxideScavenged=\frac{Atest}{Acontrol}X100$(3)

where Acontrol is the absorbance of the blank and Atest is the absorbance of the test sample. IC₅₀ values were obtained from a dose-effect curve (Gyesi et al., 2019).

2.4.2. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay

Experiments were conducted in a microtiter plate. Ascorbic acid was used as standard drug. Two hundred microliters of 0.1 mM DPPH solution prepared in methanol was added to each well. One hundred microliters of extract or standard drug at different concentrations were then added to the wells. The reaction mixture was then shaken and incubated for 30 min away from light. Absorbance was taken at 517 nm (BioTeK Synergy H1 multimode microplate reader, Germany). The control blank reaction mixture was made by replacing the extract with methanol. There were 3 replicates for each concentration. The percent DPPH radical scavenged was calculated from Equation (4)(4) $\mathrm{\%}DPPHRadicalScavenged=\left(\frac{Acontrol-Asample}{Acontrol}\right)X100$(4)

(4) $\mathrm{\%}DPPHRadicalScavenged=\left(\frac{Acontrol-Asample}{Acontrol}\right)X100$(4)

where Asample is the absorbance of sample mixture and Acontrol is the absorbance of the blank reaction mixture.

IC₅₀ values were obtained from a dose–effect curve obtained by plotting % DPPH radical scavenged against extract concentration (Borquaye et al., 2015, 2016).

2.4.3. Phosphomolybdenum (PM) assay

The total antioxidant capacity was evaluated using the phosphomolybdenum (PM) assay. The PM reagent was prepared by mixing 6 mL of concentrated sulphuric acid, 0.5 g sodium phosphate and 0.4 g ammonium molybdate together in water to a total volume of 100 mL. Ascorbic acid was used as standard drug. To 10 mL of phosphomolybdenum (PM) reagent in a test tube was added 1 mL of various concentrations of test extract or standard drug. The content of the test tubes was thoroughly mixed and incubated for 90 min at 95°C. After samples had cooled to room temperature, absorbance was read at 695 nm (Perkin Elmer Lambda 35) against a blank solution. The blank solution was made by substituting the test sample with a solvent. The total antioxidant capacity was expressed as ascorbic acid equivalent (AAE) (Ofori–Baah & Borquaye, 2019).

3. Results and discussion

3.1. Extraction

To mimic the traditional method of preparation of the plant for ethno-medical use, ethanol was chosen as the solvent for the extraction. Soxhlet extraction of the plant materials with ethanol afforded extracts in appreciable yield. The yield of the root extract was slightly higher (10.4%) than that of the stem bark (8.1%). Both yields were however similar to yields of ethanolic extracts obtained for other medicinal plants (Laryea & Borquaye, 2019).

3.2. Anti-inflammatory activity

The use of plant-derived metabolites for the treatment of inflammation-related diseases has been in existence for ages. The use of extracts from the willow tree in managing inflammatory conditions led to the isolation of the active ingredient, salicin (Vane & Botting, 1987). Aqueous extracts of Ceratonia siliqua L. are also known to have been used to treat inflammation in Arab ethnomedicine (Azab et al., 2016). However, scientific validation for the use of most medicinal plants is absent (Angell & Kassirer, 1998). In the evaluation of the anti-inflammatory properties of the stem bark and root extracts of Tamarindus indica L., the carrageenan-induced paw edema model of inflammation was used. The time course curve for both extracts and standard drugs are indicated in Figure 1(a—d). Upon administration of carrageenan, a steady rise in foot volume was observed for the first 90 min. Thereafter, extract or drug was administered. This resulted in a general decrease in foot volume until the 4^th hour. The control group, which received only saline, only observed minimal reduction in foot volume and a significant edema was observed even at the 4^th hour. The total edema, for each treatment group, was derived from the area under the curve and represented in arbitrary units in Figure 1(a’—d’). A dose-dependent effect was observed for both standard drugs and extract treatments. The ED₅₀ values obtained (Table 1) indicated that both root and stem bark extracts had promising anti-inflammatory activities, with ED₅₀ values of 118.1 and 154.5 mg/kg, respectively. The standard drugs were much superior, with ED₅₀’s of 1.2 and 17.4 mg/kg for dexamethasone and diclofenac, respectively.

Table 1. Yield of extraction and effect of extracts and standard drugs on carrageenan-induced edema

Extract	Yield (%)	ED50 ± SEM (mg/kg)
Tamarindus indica stem bark extract	8.1^a	154.5 ± 2.6
Tamarindus indica root extract	10.4^a	118.1 ± 1.9
Dexamethasone		1.2 ± 0.7
Diclofenac		17.4 ± 9.5

SEM: standard error of the mean.

^a: Yield based on powdered sample used in Soxhlet extraction.

Figure 1. Time course graphs depicting the effects of different concentrations of extracts or standard drugs on carrageenan-induced edema in chick foot (a—TISBE; b—TIRE; c—Dexamethasone; d—Diclofenac) AND the total edema response represented as the area under the curve (AUC) for extracts or standard drugs (a’—TISBE; b’—TIRE; c’—Dexamethasone; d’—Diclofenac). Values are mean ± SEM for 5 replicate experiments (n = 5). Data subjected to One-way ANOVA followed by Dunnett’s post hoc test [p > 0.05 (ns), p < 0.05 (*), p < 0.01 (**), p < 0.001 (***), compared to control group treated with normal saline] [TISBE—Tamarindus indica STEM BARK extract; TIRE—Tamarindus indica ROOT extract]

The carrageenan-induced paw edema model of inflammation is a common technique used to screen natural products with potential anti-inflammatory activity. In this model, induction of edema upon carrageenan administration is the result of synergistic action of various inflammatory mediators. Induction of inflammation following carrageenan administration proceeds via two clear phases—a first phase characterized by release of histamine and serotonin, and a second phase where inflammatory mediators such as prostaglandins, bradykinins, leukotrienes, lysosomes and proteases are released (Eddouks et al., 2012). Drugs such as diclofenac, indomethacin and aspirin exert their anti-inflammatory action by interfering with the second phase. The similarity in the time course curves between the extracts and both diclofenac and dexamethasone presupposes that the extracts may also interfere with the second phase and inhibit the release of similar inflammatory mediators.

The findings in this study are supported by works done elsewhere. The anti-inflammatory activities of the seeds, fruits, leaves and seed coat have been investigated. Bandawane et al. investigated the anti-inflammatory and analgesic activities of the seed of Tamarindus indica and demonstrated a dose-dependent activity of the leaf extracts on carrageenan-induced inflammation in rats (Bandawane et al., 2013). The methanol extract of the fruits of the plant has also been classified as possessing moderate anti-inflammatory activity (Mohammed et al., 2015) whereas the stem bark extracts were shown to possess substantial analgesic activity (Ukwuani & Hassan, 2014). Recently, Gupta and Singh showed that the aqueous and ethanolic extracts of the root of Tamarindus indica possess anti-inflammatory activity, similar to the findings of this study. The extracts were rich in tannins, saponins, glycosides, flavonoids and polyphenols and the anti-inflammatory action was attributed to these phytochemicals (Gupta & Singh, 2017). Various other activities such as antibacterial and antifungal of various parts of the plant have also been reported. Together, the findings of this study and the other studies validate the use of the plant in ethnomedicine.

3.3. Antioxidant activity

Reactive oxygen species (ROS) and other free radicals are produced during inflammation-associated cellular injuries. ROS facilitates lipid peroxidation and breakdown of many macromolecules and cause injury to tissues. As a result, inflammatory mediators are released (Geronikaki & Gavalas, 2006). This strong association between ROS, and hence oxidative stress, and inflammation led to an investigation of the antioxidant activity of the extracts. The ability of the extracts to scavenge free radicals and ROS was evaluated in the DPPH and hydrogen peroxide assays. The IC₅₀s of the stem bark extract in both the DPPH and hydrogen peroxide assays were much lower than the root extract (Table 2). In the DPPH assay, the IC₅₀’s for the stem bark and root extracts were 379.9 and 725.7 µg/mL, respectively, whereas the IC₅₀’s in the hydrogen peroxide assays were 513.9 and 1329.1 µg/mL for stem bark and root extracts, respectively. Both extracts were better scavengers of the DPPH radical than hydrogen peroxide. The total antioxidant capacity (TAC) was determined using the phosphomolybdenum assay. The TAC for the stem bark and root extracts was determined to be 27.16 and 27.29 AAE/100 g of crude extract, respectively (Table 3). Many extracts and compounds exert antioxidant action by interfering with the formation of the initiator radical or terminate radicals during chain propagation. Some antioxidants also act indirectly by enhancing the activities of enzymes that neutralize ROS or induce the expression of such proteins (Amorati et al., 2013). Since these extracts contain a number of different phytochemicals, the antioxidant effect exhibited is most likely a result of the synergistic action of the various constituents.

Table 2. DPPH radical and hydrogen peroxide scavenging activities of the ethanolic stem bark and root extracts of Tamarindus indica

Extract	DPPH Radical Scavenging Assay IC50 (µg/mL)	Hydrogen Peroxide Scavenging Assay IC50 (µg/mL)
Tamarindus indica stem bark extract	379.9 ± 9.6	513.9 ± 20.7
Tamarindus indica root extract	725.7 ± 8.9	1329.1 ± 14.8
Ascorbic Acid	42.5 ± 1.9	ND
Gallic Acid	ND	204.3 ± 3.1

ND—Not Determined.

Triplicate repeats were used in each assay.

Table 3. Total antioxidant capacity and total phenolic content of the ethanolic stem bark and root extracts of Tamarindus indica

Extract	Total Antioxidant Capacity g/100 g AAE	Total Phenolic Content g/100 g GAE
Tamarindus indica stem bark extract	27.16 ± 4.5	13.1 ± 2.3
Tamarindus indica root extract	27.29 ± 3.7	11.2 ± 3.6

Triplicate repeats were used in each assay.

The total phenolic content (TPC) of the extracts was determined using the Folin–Ciocalteu assay. Both extracts had similar phenolic contents. The TPC for the stem bark extract was 13.1 g/100 g GAE and that of the root extract was at 11.2 g/100 g GAE (Table 3). The strong similarity between TPC and TAC values of both extracts is probably due to the fact that phenolic compounds are generally good antioxidants. Phenolic compounds donate hydrogens to stabilize ROS. The resulting unpaired electron on the phenolic compound is stabilized by the aromatic ring (Miller & Ruiz-Larrea, 2002). It has therefore been suggested that there exists a positive correlation between antioxidant activity and TPC (Velioglu et al., 1998). The results of this study support this notion.

4. Conclusion

The utility of Tamarindus indica in ethnomedicine is immense. This study has shown that both root and stem bark ethanolic extracts of the plant do possess anti-inflammatory and antioxidant activities. The stem bark extract showed better activity in reducing carrageenan-induced edema in chick compared to the root extract. The stem extract also showed much better scavenging potential than the root extract. Both root and stem extract, however, had similar total antioxidant capacities and total phenolic contents. The results of this study provide further support for the use of the plant in ethnomedicine.

Competing Interests

The authors declare that there were no competing financial, professional, or personal interests that might have influenced the performance or presentation of the work described in this manuscript.

Author Contributions

The study was conceived by LSB. All experiments were designed by LSB and MSD. Plant collection and all experimental procedures were done by MSD, SOB and JAM. The data were analyzed MSD, SOB, JAM and LSB. The initial manuscript was drafted by LSB. All authors read and approved the final manuscript.

Ethics

The project proposal and procedures were reviewed and approved by the Institution Ethics Review Board for Animal Use at the Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.

Acknowledgements

Authors acknowledge support from the Departments of Chemistry and Pharmacology, all in KNUST, whose facilities were used for this study. Mr. Gyan, Bernard Ussher and Michael Konney Laryea, all of KNUST and Inusah Issah of the Department of Chemical Sciences, University of Energy and Natural Resources, Sunyani – Ghana provided technical support and are duly acknowledged.

Data availability

All data generated or analyzed during this study are included in this published article.

Additional information

Funding

No direct funding was received for this research. The rotary evaporator used for the study was purchased with an International Foundation for Science (IFS) Collaborative Research Grant to LSB.

Notes on contributors

Lawrence Sheringham Borquaye

Lawrence Sheringham Borquaye is a bioorganic chemist at the Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana and leader of the Borquaye Research Group. His research focuses on science at the interface of chemistry and biology. He has been exploring biologically active natural products from plants and marine organisms. Other research interests include the development of methods for the analysis of pharmaceutical and personal care products in the environment and the characterization of volatile (essential oils) from plant sources. Michel Selassie Doetse, Samuel Ofori – Baah and Jennifer Amo – Mensah were undergraduate Chemistry students who did their final year projects in the Borquaye Research Group. Visit us at www.borquayelab.com for more information about our research group.