Pharmaceutical importance of some promising plant species with special reference to the isolation and extraction of bioactive compounds: A review

BACKGROUND

Active principles from natural sources, in the form of extracts and natural compounds, provide an infinite number of bioactive compounds with consummate disposal of chemical diversity. These compounds and active principles are of utmost importance in the discovery of drugs of biological origin particularly, from plants.

OBJECTIVE

Development of resourceful technology for the isolation and extraction of bioactive compounds of medicinal importance is considered as an important task for researchers. There are a number of extraction, isolation, and characterization techniques currently utilized; however, most are laborious and use toxic chemicals and huge quantities of raw materials with a very low output. There are a number of abiotic and biotic factors that affects the quality and the quantity of plants bioactive compounds. Considering this the objectives of the current review is to discuss the various extraction and characterization techniques used to isolate the essential bioactive compounds from three plant species and the biotic and abiotic factors that affects the quantity and quality of the plants secondary metabolites.

METHODS

Many advanced technologies have been developed and tested for extraction, characterization, and their capacity for high yield products, and those requiring less application of toxic solvents are investigated continuously.

CONCLUSION

In this context, the present review summarizes the different types of extraction and characterization techniques utilized commercially by the food, drug, and pharmaceutical industries for better output and environmentally- and healthbenefiting products with special reference to three industrially important plants: Leonotis leonurus (L.) R.Br. (Lamiaceae) and Santalum album L. (Santalaceae) and Aloe vera (L.) Burm. f. (Aloaceae or Asphodelaceae).

A review on traditionally used South African medicinal plants, their secondary metabolites and their potential development into anticancer agents

ETHNOPHARMACOLOGICAL RELEVANCE

Approximately 70% of anticancer drugs were developed or derived from natural products or plants. Southern Africa boasts an enormous floral diversity with approximately 22,755 plant species with an estimated 3000 used as traditional medicines. In South Africa more than 27 million individuals rely on traditional medicine for healthcare. The use of South African plants for the treatment of cancer is poorly documented, however there is potential to develop anticancer agents from these plants. Limited ethnobotanical studies report the use of plants for cancer treatment in traditional medicine. Plants growing in tropical or subtropical regions, such as in South Africa, produce important secondary metabolites as a protective mechanism, which could be used to target various factors that play a key role in carcinogenesis.

AIMS

The aim was to collate information from primary ethnobotanical studies on South African plants traditionally used for the treatment of cancer. Evaluation of literature focused on traditionally used plants that have been tested for their in vitro activity against cancer cells. Secondary metabolites, previously identified within these plant species, were also included for discussion regarding their activity against cancer. The toxicity was evaluated to ascertain the therapeutic potential in further studies. Additionally, the aim was to highlight where a lack of reports were found regarding plant species with potential activity and to substantiate the need for further testing.

MATERIALS AND METHODS

A review of ethnobotanical surveys conducted in South Africa for plants used in the treatment of cancer was performed. Databases such as Science Direct, PubMed and Google Scholar, university repositories of master's dissertations and PhD theses, patents and books were used. Plant species showing significant to moderate activity were discussed regarding their toxicity. Compounds identified within these species were discussed for their activity against cancer cells and toxicity. Traditionally used plants which have not been scientifically validated for their activity against cancer were excluded.

RESULTS

Twenty plants were documented in ethnobotanical surveys as cancer treatments. Numerous scientific reports on the potential in vitro activity against cancer of these plants and the identification of secondary metabolites were found. Many of the secondary metabolites have not been tested for their activity against cancer cells or mode of action and should be considered for future studies. Lead candidates, such as the sutherlandiosides, sutherlandins, hypoxoside and pittoviridoside, were identified and should be further assessed. Toxicity studies should be included when testing plant extracts and/or secondary metabolites for their potential against cancer cells to give an indication of whether further analysis should be conducted.

CONCLUSION

There is a need to document plants used traditionally in South Africa for the treatment of cancer and to assess their safety and efficacy. Traditionally used plants have shown promising activity highlighting the importance of ethnobotanical studies and traditional knowledge. There are many opportunities to further assess these plants and secondary metabolites for their activity against cancer and their toxic effects. Pharmacokinetic studies are also not well documented within these plant extracts and should be included in studies when a lead candidate is identified.

Hepatotoxic effects of Euphol-rich fractions from Euphorbia bivonae-Relevance to cytotoxic and anti-tumor activities

These studies were designed to evaluate the preliminary oral toxicity profile of the crude ethanolic aerial part extract of E. bivonae in the Male albino Wistar rats and its active chemical constituents. The 24-h LD₅₀ was determined using probit analysis method. The single dose LD₅₀was found to be 2568.64 mg/kg bw when administrated orally in mice. Additionally, the Wistar rats were used to evaluate the subchronic toxicity of E. bivonae ethanolic extract. The serum biomarkers, lipid peroxidation and antioxidants status in liver and histopathological analysis were investigated in normal and treated groups. Subchronic toxicity studies in rats with oral doses of 50, 150, 350 and 500 mg/kg body weight showed significant increase in alanine aminotransferase, aspartate aminotransferase and total bilirubin levels. In addition, the administration of this extract significantly (p < 0.05) decreased superoxide dismutase, catalase and glutathione peroxidase and an increment in lipid peroxidation and protein carbonyls. Finally, we suggest that the three compounds of E. bivonae extract (sitosterol, euphol and lupeol) are the mainly responsible of this toxicity.

Ethnobotanical survey of medicinal plants used to manage High Blood Pressure and Type 2 Diabetes Mellitus in Bitterfontein, Western Cape Province, South Africa

ETHNOPHARMACOLOGICAL RELEVANCE

The aim of this study was to identify and document medicinal plants used to manage High Blood Pressure and Type 2 Diabetes Mellitus in Bitterfontein, Western Cape Province, South Africa.

METHODS

One hundred and twelve (112) respondents were interviewed between August 2014 and September 2015 through semi-structured surveys to gather data on the percentage of people who had been diagnosed with High Blood Pressure and/or Type 2 Diabetes Mellitus and to determine the frequency of medicinal plant and allopathic medicine use. Twelve (12) key respondents were subsequently selected, using a non-probability snowball sampling method. They were interviewed in-depth concerning their plant practices and assisted with plant collection.

RESULTS

Twenty-four plant (24) species belonging to 15 families were identified for the management of High Blood Pressure and Type 2 Diabetes Mellitus. The most frequently reported families were Asteraceae (20.8%), Lamiaceae (16.67%), Crassulaceae (8.33%) and Aizoaceae (8.33%). The remaining (45.54%) were evenly split over eleven families- Fabaceae, Amaryllidaceae, Anacardiaceae, Capparaceae, Geraniaceae, Apiaceae, Convolvulaceae, Apocynaceae, Rutaceae, Asphodelaceae and Thymelaeaceae. The most commonly used plant species overall was Lessertia frutescens (96.55%). The most frequently used plant parts included leaves (57.63%) roots/bulbs (15.25%) and stems (11.86%), mostly prepared as infusions or decoctions for oral administration.

CONCLUSIONS

Medicinal plants are widely used by High Blood Pressure and Type 2 Diabetes Mellitus sufferers. They employ diverse plant species to manage both conditions. In addition, some sufferers often use prescribed allopathic medication, as well as medicinal plants, but at different intervals. Despite high usage the plants identified are not currently threatened (Red Data list status: least concern).

"Wild cannabis": A review of the traditional use and phytochemistry of Leonotis leonurus

ETHNOPHARMACOLOGICAL RELEVANCE

Leonotis leonurus, locally commonly known as "wilde dagga" (=wild cannabis), is traditionally used as a decoction, both topically and orally, in the treatment of a wide variety of conditions such as haemorrhoids, eczema, skin rashes, boils, itching, muscular cramps, headache, epilepsy, chest infections, constipation, spider and snake bites. The dried leaves and flowers are also smoked to relieve epilepsy. The leaves and flowers are reported to produce a mild euphoric effect when smoked and have been said to have a similar, although less potent, psychoactive effect to cannabis.

AIM OF THE REVIEW

To amalgamate the botanical aspects, ethnopharmacology, phytochemistry, biological activity, toxicity and commercial aspects of the scientific literature available on L. leonurus.

METHODS

An extensive review of the literature from 1900 to 2015 was carried out. Electronic databases including Scopus, SciFinder, Pubmed, Google Scholar and Google were used as data sources. All abstracts, full-text articles and books written in English were considered.

RESULTS

The phytochemistry of particularly the non-volatile constituents of L. leonurus has been comprehensively investigated due to interest generated as a result of the wide variety of biological effects reported for this plant. More than 50 compounds have been isolated and characterised. L. leonurus contains mainly terpenoids, particularly labdane diterpenes, the major diterpene reported is marrubiin. Various other compounds have been reported by some authors to have been isolated from the plant, including, in the popular literature only, the mildly psychoactive alkaloid, leonurine. Leonurine has however, never been reported by any scientific analysis of the extracts of L. leonurus.

CONCLUSION

Despite the publication of various papers on L. leonurus, there is still, however, the need for definitive research and clarification of other compounds, including alkaloids and essential oils from L. leonurus, as well as from other plant parts, such as the roots which are extensively used in traditional medicine. The traditional use by smoking also requires further investigation as to how the chemistry and activity are affected by this form of administration. Research has proven the psychoactive effects of the crude extract of L. leonurus, but confirmation of the presence of psychoactive compounds, as well as isolation and characterization, is still required. Deliberate adulteration of L. leonurus with synthetic cannabinoids has been reported recently, in an attempt to facilitate the marketing of these illegal substances, highlighting the necessity for refinement of appropriate quality control processes to ensure safety and quality. Much work is therefore still required on the aspect of quality control to ensure safety, quality and efficacy of the product supplied to patients, as this plant is widely used in South Africa as a traditional medicine. Commercially available plant sources provide a viable option for phytochemical research, particularly with regard to the appropriate validation of the plant material (taxonomy) in order to identify and delimit closely related species such as L. leonurus and L. nepetifolia which are very similar in habit.

In vivo Studies on Antidiabetic Plants Used in South African Herbal Medicine

Diabetes is one of the most common metabolic disorders worldwide. It is a major health problem with its frequency increasing every day in most countries. The disease is generally believed to be incurable; and the few orthodox drugs available to manage the disease are not readily affordable to the poor. Based on the historical success of natural products as antidiabetic agents and the ever increasing need for new antidiabetics, a number of South African medicinal plants have been evaluated for their antidiabetic properties. In this article, we review the major studies conducted based on ethnobotanical surveys carried out between 2005 and 2008 in South Africa on plants that are traditionally used for the treatment of diabetes. Overall, the results of the studies conducted confirmed the potential of South African medicinal plants in antidiabetic drug discovery and identified a number of promising taxa for further in vivo investigation as plant-based antidiabetic agents.

Effect of aqueous extract of Leonotis leonurus (L.) R. Br. leaves in male Wistar rats

The aqueous extract of the leaves of Leonotis leonurus (L.) R. Br. at the doses of 125, 250 and 500 mg/kg body weight was investigated for toxicity in male rats following administration on daily basis for 21 days. The extract did not significantly (p > .05) alter the levels of haemoglobin, packed cell volume, mean corpuscular volume, red cell distribution width, basophils, total protein, phosphorus, calcium and chloride ions of the animals. Whereas the levels of lymphocytes, eosinophils, monocytes, triacylglycerol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, atherogenic index, albumin as well as alkaline phosphatase and gamma glutamyl transferase activity were decreased by the extract, those of neutrophil, magnesium, total and conjugated bilirubin, alanine and aspartate aminotransferase as well as liver and kidney body weight ratios increased. There was decrease in the mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration and cholesterol only at the 500 mg/kg body weight of the extract, whereas the large unstained cells, sodium ions, white blood cells and uric acid increased only at 250 and 500 mg/kg body weight of the extract, respectively. The urea, creatinine and potassium increased only at 125 mg/kg body weight of the extract while the globulin content was elevated only at 500 mg/kg body weight of the extract. The doses did not produce any definite pattern of effect on the red blood cells and platelets. These alterations by the aqueous extract of L. leonurus leaves on the haematological together with the liver and kidney functional indices suggests parameter and dose-selective effects of the extract and will have consequential effects on the normal functioning of the blood system, kidney and liver of the animals. The extract is also unlikely to predispose the animals to cardiovascular risk when repeatedly consumed on daily basis at the doses investigated for 21 days. Therefore, the aqueous extract of L. leonurus leaves may not be 'safe' as oral remedy in male rats.

Ovicidal and larvicidal activity of crude extracts of Melia azedarach against Haemonchus contortus (Strongylida)

The rapid development of anthelmintic resistance, associated with the high cost of the available anthelmintic drugs, has limited the success of gastrointestinal nematodiosis control in sheep and goats and thus created interest in studying medicinal plants as an alternative source of anthelmintics. The aim of this study was carried out to evaluate the anthelmintic activity of the leaves and seed aqueous and hydro-alcoholic extracts of Melia azedarach L. (Meliaceae) were tested for in vitro ovicidal and larvicidal activity against Haemonchus contortus (Strongylida). Both extracts were evaluated at five concentrations: 12.5, 6.2, 3.12, 1.56, and 0.78 mg/ml. The leaves aqueous and hydro-alcoholic extracts inhibited 99.4% and 100% of the egg hatching and 100% of larval development at 12.5 mg/ml, respectively. In a similar way, the leaves hydro-alcoholic extract was the most active on egg inhibition (ED (50) = 1.97 and ED ( 90 ) = 5.05 mg/ml), leaves and seed aqueous and hydro-alcoholic extracts showed the best inhibition of larval development (ED ( 50 ) = 3.01, 2.43, 3.17, 2.40, and ED ( 90 ) = 10.53, 8.14, 11.94, and 8.19 mg/ml), respectively. These results suggest that utilization of M. azedarach extracts is useful in the control of H. contortus.

In-vitro anthelminthic activity of crude aqueous extracts of Aloe ferox, Leonotis leonurus and Elephantorrhiza elephantina against Haemonchus contortus

Aloe ferox (Mill), Leonotis leonurus (L) R. BR; and Elephantorrhiza elephantina (Burch.) Skeels are plants frequently used by resource-limited farmers in the Eastern Cape Province to control gastrointestinal parasites in goats. A study was conducted to validate their anthelminthic activities in-vitro on the egg and larvae of the nematode parasite Haemonchus contortus. The crude aqueous extracts of leaves of A. ferox and L. leonurus; and roots of E. elephantina were used. Eggs and larvae of the parasite were incubated at 25 degrees C in aqueous extracts at concentrations of 0.625-20 mg/ml for 48 h and 7 days for the egg hatch and larval development assays respectively. Albendazole and water were the positive and negative controls respectively. Inhibition of egg hatching and larval development increased significantly (P < 0.05) with increasing concentrations of the extracts. E. elephantina and L. leonurus extracts had 100% egg hatch inhibition at concentration as low as 2.5 mg/ml and 1.25 mg/ml respectively, whereas A. ferox extracts had 100% inhibition at concentrations of 20 mg/ml. At the lowest concentration tested (0.625 mg/ml), E. elephantina inhibited egg hatching >96% and this was comparable to albendazole at the same concentration. E. elephantina and L. leonurus also totally inhibited larval development at concentrations of 1.25 mg/ml. The study provided evidence that A. ferox, E. elephantina and L. leonurus extracts possess anthelminthic activity, thus justifying their use in the treatment of GI helminthosis. There is however need to assess the safety of these plants in vivo and also to undertake in vivo efficacy studies.