Sudan traditional medicine is characterized  by  a  unique combination  of  Islamic, Arabic,  and  African  cultures. In poor communities, traditional medicine has remained as the most reasonable source of treatment of several diseases and microbial infections. Although the traditional medicine is accepted in Sudan, to date there is no updated review available which focuses on most effective and frequently used Sudanese medicinal plants (Karar and Kuhnert, 2017).

Adansonia digitata (Bombacaceae) known as Baobab is an important plant used in Sudanese traditional medicine; it is widespread throughout the hot, drier regions of tropical Africa. It extends from northern Transvaal and Namibia to Ethiopia and Sudan. In Sudan, the baobab is most frequently found on sandy soils and by seasonal streams Khors in short grass savannas. It forms belts in Central Sudan, Kordofan, Darfur and Blue Nile (Dabora, 2016). The Baobab fruit pulp is an important foodstuff used as a drink, a sauce for food and as a fermenting agent in local brewing (Gebauer et al., 2002). Different parts of the plant are used to treat many diseases. The alkaloid ‘adansonin’ in the bark is thought to be the active principle for treatment of malaria and other fevers (De Caluwé et al., 2010). The plant is: Anti-oxidizing agent including; polyphenolic compounds, vitamins E and C, cardiovascular diseases, cancer and aging related disorders (De Caluwé et al., 2010); antiviral activity against Herpes simplex, Sindbis and Polio (Anani et al., 2000); anti-inflammatory and antipyretic activity (Kaboré et al., 2011); anti-microbial activity and anti-trypanosoma activity (Varudharaj et al., 2015). Tamarindus indica (Fabaceae) grows wild in Africa in locales as diverse as Sudan, Cameroon, Nigeria, and Tanzania (Havinga et al., 2010). Tamarind fruit pulp is used for seasoning as a food component to flavour confections, curries and sauces, and is a main component in juices and certain beverages. Tamarind fruit pulp is eaten fresh and often made into a juice, infusion or brine, and can also be processed into jam and sweets (Hassan, 2014). The plant is widely used in African traditional medicine for treatment of many diseases such as fever, dysentery, jaundice, gonococci and gastrointestinal disorders (Lawal et al., 2010). Phytochemical investigation carried out revealed the presence of many active constituents, such as phenolic compounds, cardiac glycosides , L-(-)mallic acid, tartaric acid, the mucilage and pectin, arabinose, xylose, galactose, glucose, and uronic acid. The ethanolic extracts showed the presence of fatty acids and various essential elements like arsenic, calcium, cadmium, copper, iron, sodium, manganese, magnesium, potassium, phosphorus, lead, and zinc (Bhadoriya et al., 2011). Many studies have been performed on skin, eye and   respiratory   tract   irritation   mediated   by  complex mixtures, but only few studies allows a quantitative evaluation of the modulating effects of the combination of single chemicals. Further studies on the modulating effects of the combination of chemicals concerning skin, eye and respiratory tract irritation will be required in order to evaluate the possibilities for synergistic or antagonistic effects being mediated by mixtures of chemicals (Doty et al., 2004). The present study reports the effect of blending equal amounts of A. digitata (Bombacaceae) and T. indica (Fabaceae) fruit, leaf and bark 96% ethanolic extract on their antioxidant, anti-inflammatory and antimicrobial activities.

Anti-inflammatory activity

Inhibition of albumin denaturation

Inhibition of protein denaturation was evaluated by the method of Mizushima and Kobayashi with slight modification: 500 μL of 1% bovine serum albumin was added to 100 μL of plant extract with different concentrations. This mixture was kept at room temperature for 10 min, followed by heating at 51°C for 20 min. The absorbance was recorded at 660 nm. (Chandra et al., 2012). Percent inhibition for protein denaturation was calculated using:

Where A0 is the absorbance of the control and A1 is the absorbance of the sample.

Antimicrobial activity

Test microorganisms

Bacteria organisms used were Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Salmonella typhi. The fungal organisms used were Candida albicans and Aspergillus niger. Standard strains of microorganism used in this study were obtained from medicinal and aromatic plants research institute.

Antibacterial assay

The disc-diffusion assay with some modifications was employed to investigate the inhibition of bacterial growth by plants extract (Kil et al., 2009). Extract solution (20 mg/ml) was prepared by diluting with dimethyl sulfoxide (DMSO) 30%. Base plates were prepared by pouring 10 ml Mueller-Hinton (MH) agar into sterile Petri dishes. About 0.1 ml of the standardized bacterial stock suspension 10⁸ to 10⁹ C.F.U/ ml were streaked on Mueller Hinton agar medium plates using sterile cotton swab. Sterilized filter paper disc (6 mm diameter) were soaked in the prepared extracts, and then were placed on the surface of the test  bacteria  plates.  The  plates  were incubated for 24 h and the diameters of the inhibition zones were measured.

Antifungal assay

The same method described for bacteria was employed to assess antifungal activity, Sabouraud Dextrose Agar was used. The inoculated medium was incubated at 25ËšC for two days for the C. albicans and three days for A. niger.

Extraction of the plants

Among the extracts obtained using 96% ethanol, T. indica fruits gave the highest yield of 22.84% as shown in Table 1, leaf extracts of both plants gave the same yield of 14%, while the bark extract of A. digitata gave the lowest yield of 1.9%.

Phytochemical screening of T. indica and A. digitata

The extracts of T. indica contained some secondary metabolites; most of them present in leaves and bark including alkaloids, flavonoids, glycosides, terpenoids, coumarins, tannins, saponins, reducing sugars and carbohydrates. Antibacterial activity of Tamarind leaf extract was attributed to the presence of flavonoids, alkaloids, tannins, cyanogenic glycosides and anthraquinones. It is known that these phytochemicals and some other aromatic secondary metabolites may serve as natural agents that protect plants against microbial pathogens and insect predators. Phytochemicals may act like antioxidants to facilitate, protect and regenerate essential nutrients and/or work to deactivate cancer-causing substances (Gomathi et al., 2017). The results of the phytochemical screening showed that A. digitata fruit, leaf and bark extracts were rich in alkaloids, flavonoides, sterols, triterpines, tannins, saponins, coumarins, glycosides, reducing sugar and carbohydrates in all parts, but anthraquinones were not detected (Table 2). Many of these are known to provide protection against insects’ attacks and plant diseases. The results obtained seems to justify the use of leaf of A. digitata in African dishes as it contained appreciable amount of some important compounds such as phenols, saponins, flavonoids, alkaloids. It is also possible that these plant species could have allelopathy effect on other organisms in their ecotype since these bioactive substances are responsible for such actions. Cardiac glycoside detected in this plant indicated that the plant could be a good source for birds and insect repellants (Lock et al., 2016).    

Antioxidant activity

DPPH radical scavenging activity

The in vitro antioxidant activity of fruit, leaf and bark ethanolic  extracts   of   T.   indica   and   A.  digitata  was evaluated using DPPH assay. Results are shown in Figure 1. The highest result of antioxidant activity by DPPH scavenging assay in fruit extract in Tamarind (84.07%) followed by Baobab (83.98%). The result is very high compared with ascorbic acid (93.5%) as antioxidant  standard.  The leaves  of Tamarind showed higher activity (61.66%) than Baobab (15.69 %), whereas the bark showed 51.48 and 66.90% in Tamarind and Baobab respectively. Several reports indicated that the antioxidant potential of medicinal plants may be related to the concentration of their phenolic compounds which include phenolic acids, flavonoids, anthocyanins and tannins (Djeridane et al., 2006; Wong et al., 2006). The health benefit of fruits are mainly attributed to phenolic compounds and vitamins, which enhance their antioxidant, anticancer, anti-mutagenic, antimicrobial, anti-inflammatory and neuroprotective properties. Bio-guided fractionation of extracts might promote the development of alternative therapeutic compounds for the prevention and treatment of various diseases and disorders.

In this study different part of A. digitata and T. indica were used. The plants are rich sources of chemical and bioactive compounds including therapeutic and dietary constituents. The present study suggests that blending of the plants parts of A. digitata and T. indica could be a potential   source     of     natural    antioxidant    and  anti-inflammatory properties that could have great importance in the inhibition of inflammation as well as against bacterial and fungal infections. The findings of this study suggest that the tested plants and their combinations can be developed as effective herbal phyto-pharmaceutical drugs for treatment and nutrition. Based on the research outcomes we recommend conducting more experiments on the combination such as anticancer activity, bacterial and fungal infections and virus infections.

The authors have not declared any con­flict of Interests.

The present work is the second part of devoted interdepartmental on-going research in the Faculty of Pharmacy, UMST. The authors are grateful to the dean of the Faculty of Pharmacy Prof. Abdelazim Elshaikh and to the administration of the UMST for their support.