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Plectranthus
species
Solvent of
Extraction
P. ternifolius mixture
P. verticillatus aqueouslv
Other Activities Reference
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impairment
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Alzheimers disease
Guo et al., 2006
Fale et al., 2009
NB. Coleus species are also included in this table because of the uncertain relationship to the Plectranthus
species
* Unknown species
Key: lv: leaves, rt: roots, s: stems, a: aerial parts, w: whole plant, f: flowers
2.4 The phytochemistry of Plectranthus
The main phytochemical constituents of Plectranthus are diterpenoids, with about one-
hundred and forty-seven of these compounds being isolated from the coloured leaf-glands
of Plectranthus species, the majority of which were highly modified abietanoids.
Essential oils, monoterpenoids, sesquitepenoids and phenolics have also been isolated
from Plectranthus species (Abdel-Mogib et al., 2002; Lukhoba et al., 2006).
Compounds 27 to 174 are grouped into five categories, the royleoanone-type abietanes
(compounds 27 to 69), the spirocoleons (compounds 70 to 108), vinylogous quinones
(compounds 109 to 130), coleon-type abietanes (compounds 131 to 167) and the
miscellaneous abietanes (compounds 168 to 174) which do not resemble any of the
abietanes in the previous four categories.
Twenty royleanone type abietanes with the presence of a hydroxybenzoquinone or p-
quinoid ring C system and an isopropyl group at C-13 have been isolated from eleven
known Plectranthus species and three Coleus species (Table 6a). These compounds all
have methyl groups at C-4 and C-10 with the exception of compound 42 where the
methyl group at C-10 is oxidized to an alcohol. Compound 45 is notably different from
compounds 27 to 46, as the substituent at C-12 is an acetyl group. At C-6 and C-7 of
compounds 27 to 42, there are either hydroxy, aldehyde or acetyl groups attached to these
positions, with the substituent at C-6 being in the beta position. In compounds 43 to 46,
39