Abstract
The family Asteraceae is one of the largest flowering plant families in South Africa and
the ongoing research on the species of this family continues to provide new insights from an
ethnobotanical and pharmacognostic perspective. Although there are many publications on
ethnobotanically relevant members of the family, some species have remained poorly studied.
This study focussed on some of these scientifically poorly studied species, namely Myrovernix
glandulosus, Plecostachys polifolia, Plecostachys serpyllifolia, Seriphium cinereum,
Seriphium incanum, Seriphium plumosum and Tenrhynea phylicifolia.
In the current study, leaf anatomical characters of potential diagnostic value, the
chemical composition of essential oil (by gas chromatography-mass spectrometry) and the
antimicrobial activity of crude extracts (minimum inhibitory concentrations: MIC) were studied
for all the selected species. Also reported here is an exploratory study of phenolic compounds
in Plecostachys species and Tenrhynea, using high performance liquid chromatography.
Myrovernix glandulosus
This medicinal plant has been reported as a good anthelmintic and was used to treat
heart related problems by the Cape people. The anatomical study revealed potential
taxonomically useful characters that could be used in distinguishing the species from its sister
taxa. The leaves are ericoid and scale-like, with a concave adaxial side enveloping the stem,
and gibbose abaxial side with prominent keel facing on the outside. The major essential oil
components identified from this species include spathulenol, viridiflorol and sabinene.
Moderate activity was observed against Aeromonas hydrophila.
Plecostachys polifolia, P. serpyllifolia and Tenrhynea phylicifolia
Plecostachys polifolia and P. serpyllifolia are two aromatic species that make up the
genus Plecostachys. While there is minimal published information on P. polifolia, the
ethnobotanical uses, essential oil composition and antimicrobial activity for P. serpyllifolia is
known but requires elaboration. Plecostachys serpyllifolia is traditionally used for respiratory
ailments and as a pleasant tasting tea. The anatomical study revealed taxonomically useful
characters and showed similarities between Plecostachys and the monotypical, southern
African endemic genus Tenrhynea. An exploratory study of phenolic compounds in several
populations of the three species (Plecostachys polifolia, P. serpyllifolia and Tenrhynea
phylicifolia) showed that they can easily be identified by the combination of the three main
compounds. These show a diagnostically different pattern in all the samples and species
studied. While all three species accumulate 3,4-dicaffeoylquinic acid, a yet unidentified
vi
compound is confined to P. serpyllifolia and 1,4,5-tricaffeoyl-3-methoxyoxaloylquinic is unique
to Tenrhynea phylicifolia. 3,4-Dicaffeoylquinic acid has reported antioxidant activities, which
may explain the medicinal use of Plecostachys serpyllifolia and Tenrhynea phylicifolia. The oil
composition was similar between the two species of Plecostachys and also similar when
compared to the main compounds in Tenrhynea. The major components were Ecaryophyllene,
α-phellandrene and sabinene. Minor components included linalool, γ-
cadinene, E-nerolidol and several others. Organic extracts of P. serpyllifolia showed moderate
activity against Klebsiella pneumoniae and Staphylococcus aureus, while water extracts of P.
polifolia showed moderate activity against Klebsiella pneumoniae.
Seriphium cinereum, S. incanum and S. plumosum
These species are widely used in traditional medicine to target gynaecological and
intestinal related disorders. The mesophyll arrangement in the leaf anatomy was found to be
comparable to that of Myrovernix glandulosus. The leaves of the three species are ericoid,
scale-like, dorsiventral, with inverted arrangement of mesophyll. The adaxial side of the leaves
is concave, adjacent to the stem, while the abaxial side is convex, without a prominent keel.
The major essential oil components identified included α-phellandrene, p-cymene and
limonene from S. cinereum; sabinene, p-cymene, limonene, β-phellandrene, citronellyl acetate
and spathulenol from S. incanum; and α-phellandrene, p-cymene, terpinene-4-ol, and
spathulenol from S. plumosum. The organic extract of all three species demonstrated
moderate activity against Candida glabrata. However, variation was evidence between
species of Seriphium, where the S. plumosum extract demonstrated noteworthy activity
against Aeromonas hydrophila, whereas only moderate activity was observed using the
extract of S. cinereum. In conclusion, some species from Seriphium may be useful in the
treatment of gynaecological infections where the infective organism is Aeromonas hydrophila.