Indigenous Salvia species : an investigation of their pharmacological activities and phytochemistry
Date
2008-09-26T07:03:36Z
Authors
Kamatou, Guy Paulin Poungoue
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Abstract
The genus Salvia belongs to the family Lamiaceae and encompasses 900 species
worldwide of which 26 are found in southern Africa and many of them are used in local
traditional medicine. However, the phytochemistry and pharmacological activities of the
South African species have not been extensively investigated.
The leaf trichome morphology that may be used to distinguish species was investigated
with the scanning electron and light microscopy. Both glandular (capitate or peltate) and
non-glandular trichomes were identified in all species.
The essential oils were isolated by hydro-distillation and analysed by GC and GC-MS
methods. The oil yield was relatively low and ranged from 0.004 (S. radula) to 0.50% (S.
muirii) (w/w). Major components identified include α-pinene, 1,8-cineole, linalool,
limonene, myrcene, β-caryophyllene, spathulenol, β-caryophyllene oxide, viridiflorol, δ-3-
carene and α-bisabolol. High performance liquid chromatography analysis was used to
identify phenolic compounds in 17 solvent extracts. Betulafolientriol oxide was detected
in all species. Rosmarinic acid was only absent in S. verbenaca, while S. garipensis and S.
radula were the only species which lacked oleanolic acid/ursolic acid.
Various in vitro biological activities were investigated. Nearly all the solvent extracts
displayed anti-oxidant activity with IC50 values ranging from 1.61 to 74.50 μg/ml using the
DPPH· radical, while the IC50 values ranged from 11.88 to 69.26 μg/ml with the ABTS·+
radical. The solvent extract of S. schlechteri was three times more active than vitamin C.
Total phenolic content based on gallic acid equivalents (GAE) revealed the presence of
total soluble phenolics in the extract at 45 to 211 mg of GAE dry sample. Almost all the
essential oils exhibited promising anti-inflammatory activity (5-lipoxygenase assay) with
IC50 values ranging from 22.81 to 77.32 μg/ml. The antimalarial activity was determined
using [3H]-hypoxanthine method on the Plasmodium falciparum (FCR-3) strain. The IC50
values of the essential oils ranged from 1.20 to 13.50 μg/ml and were low compared to the
solvent extracts (IC50 values ranging from 3.91 to 26.01 μg/ml). Betulafolientriol oxide
and salvigenin isolated from S. radula inhibited the growth of malaria parasites with IC50
values of 4.95 and 24.60 μg/ml, respectively. With the exception of S. radula, all the
solvent extracts displayed moderate to good activity against Staphylococcus aureus,
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Bacillus cereus, Klebsiella pneumoniae, Escherichia coli and Mycobacterium tuberculosis
with the MIC values ranging from 0.03 to 8.00 mg/ml. Four compounds, namely carnosol,
7-O-methylepirosmanol, oleanolic acid and its isomer ursolic acid were isolated from S.
chamelaeagnea as the active principles against S. aureus. The solvent extracts of Salvia
species were tested for in vitro anticancer activity against human breast adenocarcinoma
(MCF-7), colon adenocarcinoma (HT-29) and glioblastoma (SF-268) using the
sulforhodamine B assay. The extracts inhibited cell proliferation of all three cell lines to
varying degrees, with the IC50 values ranging between 9.69 and 43.65 μg/ml and 8.72 and
59.12 μg/ml against the MCF-7 and SF-268 cell lines, respectively. The IC50 values
against the HT-29 cell line ranged from 17.05 to 57.00 μg/ml. The in vitro toxicity profile
of 28 samples (17 solvent extracts and 11 essential oils) was evaluated on human kidney
epithelial cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5 dimethyl tetrazolium bromide
method. The samples displayed some degree of toxicity with IC50 values ranging from
1.79 to 22.9 μg/ml for the essential oils and from 12.12 to 53.34 μg/ml for the solvent
extracts. The essential oil composition of S. africana-caerulea, S. africana-lutea and S.
lanceolata, collected at the same locality throughout the 2004/2005 growing season, was
compared in terms of essential oil yields, chemical composition and biological activities.
Mostly quantitative, rather than qualitative variation was observed. Major seasonal
fluctuations of certain essential oil compounds were observed in all three species.
Variations in biological activities of the solvent extracts over seasons were noted. The
biological activities of the solvent extracts of three Salvia species (Salvia africanacaerulea,
S. africana-lutea and S. lanceolata) were evaluated in the presence and absence
of essential oils. The solvent extract of S. africana-caerulea without essential oil exhibited
the best activity against Gram-positive bacteria (MIC value: 0.1 mg/ml), while the solvent
extract containing essential oil of S. africana-lutea was the most active against Gramnegative
bacteria. The toxicity profile of all three species was significantly higher (P <
0.05) with the solvent extracts containing essential oils. The in vitro biological activities
add scientific support to the use of Salvia species in traditional medicine.
Description
Keywords
Salvia, pharmacological activities, phytochemistry