Pharmacological screening of traditional medicinal plants used against skin ailments in the Free State, South Africa
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Date
2016-06
Authors
Xaba, Valeria Makhosazana
Journal Title
Journal ISSN
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Publisher
University of the Free State (Qwaqwa Campus)
Abstract
The skin is the largest organ of the body and it is protected by a composition of
layers. It consists of three main protective layers namely epidermis, dermis and
subcutaneous layer, also known as a fat layer. Its most crucial function is playing a
key immunity role in protecting the body by forming a part of a defence and
mechanical barrier to the surrounding environment, and thereby preventing invasion
by pathogens. The skin is colonized by indigenous microbial flora which comprises of
a broad variety of species, among them are Staphylococccus sp., Propionibacteria,
Diptheroids, Micrococcus, Bacillus species and some fungal species which sustain
the health of the skin. The skin can still be susceptible to injuries that allow
opportunistic microbial agents to enter the skin. Skin diseases vary from mild
conditions which are likely to have an effect on the skin’s appearance and can lead
to severe conditions which cause disfigurement, disability, and distress or even lead
to death. An ethnobotanical survey was conducted and plants used against skin
infections were collected and documented. Bark, stem, roots, rhizomes, corms and
bulbs were reported to be the most commonly used plant parts. The survey indicated
an oral intake of the decoction or concoction preparation. The study documented 22
plant species used by the traditional healers and herbalists of the Free State
Province of South Africa for the treatment of wounds and skin infections. Eight
frequently used plants, namely Pentanisia prunelloides, Cotyledon orbiculata,
Hermannia depressa, Dioscorea sylvatica, Lycopodium clavatum, Merwilla plumbea,
Eucomis bicolar, Eucomis autumnalis and Xysmalobium undulatum were
investigated for the presence of secondary metabolites, antimicrobial, antioxidant
and anti-inflammatory properties.
Most plant species tested positive for the presence of saponins, flavonoids, tannins
and terpenoids. Saponins were detected in Pentanisia prunelloides extracts,
Hermannia depressa and Cotyledon orbiculata aqueous stem extracts, and
Xysmalobium undulatum aqueous and ethanol extracts. Flavonoids were present in
almost all plants, particularly P. prunelloides aqueous and ethanol extracts, and
aqueous extracts prepared from H. depressa, X. undulatum, and C. orbiculata stem.
Tannins were detected in aqueous, ethanol, methanol and acetone extracts
prepared from C. orbiculata stem, P. prunelloides and H. depressa. P. prunelloides
showed a high content of total flavonoids (40.43%), total alkaloids (84.8%), and
saponins (19%). Tannins had an absorbance value of 16.54 mg. Total contents
found in H. depressa were flavonoids (9.70%), alkaloids (7.0%) and saponins (5%).
X. undulatum showed small and limited amounts of total content values, flavonoids
(4.50%), alkaloids (6.7%), and saponins (9%). The presence of most general
phytochemicals might be responsible for the plants’ therapeutic and pharmacological
effects.
P. prunelloides ethanolic extract showed the best activity against Bacillus pumilus
and Staphyloccocus aureus (0.098-0.52 mg/ml). Methanol extracts showed the least
activity, but a progressive inhibition of 0.325 mg/ml against P. aeruginosa was
observed. H. depressa acetone extract showed the best activity against B. pumilus
at 0.098 mg/ml. Aqueous extract displayed good activity against E. coli, S. aureus
and P. aeruginosa with the MIC values of 0.098, 0.36 and 0.195 mg/ml, respectively.
Lycopodium clavatum acetone extract displayed good minimum inhibition against S.
aureus (0.39 mg/ml), and against P. aeruginosa (0.098 mg/ml).
Concerning antifungal activity, the best inhibition was observed with P. prunelloides
organic solvents (0.049 mg/ml). H. depressa extracts also showed low MIC values
(0.049 mg/ml-0.33 mg/ml).
The total phenolic content was determined and recorded as gallic acid equivalents.
Extracts that showed the highest phenolic content were H. depressa, C. orbiculata,
Dioscorea slyvatica, Eutumnalis bicolar and L. clavatum. H. depressa methanolic
extract had the highest phenolic content at 2.09±0.07 mg GAE/g, followed by C.
orbiculata acetone extract at 1.48±0.64 mg GAE/g. Acetone and ethanol extracts of
E. bicolar and L. clavatum displayed good total phenolic content ranging from
0.92±0.13 to 1.50±0.13 mg GAE/g. For DPPH scavenging activity, C. orbiculata
methanol extract with an IC50 value of 0.10±0.03 μg/ml, followed by D. slyvatica
aqueous extract (0.12±0.03 μg/ml). The total capacity of antioxidant using
Phosphomolybdenum assay was also investigated with gallic acid as a frame of
reference. The best activity was found in D. sylvatica ethanol extracts with an IC50
value of 0.04±0.03 μg/ml. Concerning anti-inflammatory activity using 5-
Lipoxygenase assay, L. clavatum and C. orbiculata exhibited a higher antiinflammatory
activity than that of NDGA and inhibited 5-LOX. L. clavatum ethanol
extract displayed the best activity (0.02±0.08 μg/ml). C. orbiculata ethanol extract
also exhibited great activity at 0.09±0.02 μg/ml.
Description
Keywords
Antibiotic resistance, Medicinal plant use, Antimicrobial, Antioxidant and anti-inflammatory, Medicinal plants -- South Africa -- Free State, Skin -- Diseases, Dissertation (M.Sc. (Plant Sciences))--University of the Free State (Qwaqwa Campus), 2016