Abstract:
The plant kingdom contributes significantly to the natural products that are used for the
treatment of a large number of ailments and disease across the globe. Included in these
species is the Helichrysum genus (Asteraceae), which comprises of more then 600
species across Africa of which 244 species are found in South Africa. Helichrysum
species are used in many cases for the treatment of coughs, colds, fever, infection,
headaches, menstrual pain and are also very popular for wound dressing due to their
potential antibacterial properties. The most common Helichrysum species used in
traditional medicine and for several medicinal purposes are H. cymosum, H. odoratissimum, H. petiolare and H. nudifolium. Previously published research has
shown that several of the Helichrysum species do have antimicrobial activity with the
most relevant to this study being the discovery of antiviral activity of H. aureonitens
against herpes simplex virus type 1 (HSV-1) as well as the reports of anti-HIV (human
immunodeficiency virus) activity of several Helichrysum species. With this knowledge, a
more in-depth study was initiated to identify the possible active constituents in South
African Helichrysum species against HIV. Due to the need to speed up drug discovery
especially against epidemic diseases like HIV, this study investigated a new tool
(nuclear magnetic resonance (NMR) – based metabolomics) to speed up drug
discovery form natural products especially when anti-viral constituents are investigated. odoratissimum, H. petiolare and H. nudifolium. Previously published research has
shown that several of the Helichrysum species do have antimicrobial activity with the
most relevant to this study being the discovery of antiviral activity of H. aureonitens
against herpes simplex virus type 1 (HSV-1) as well as the reports of anti-HIV (human
immunodeficiency virus) activity of several Helichrysum species. With this knowledge, a
more in-depth study was initiated to identify the possible active constituents in South
African Helichrysum species against HIV. Due to the need to speed up drug discovery
especially against epidemic diseases like HIV, this study investigated a new tool
(nuclear magnetic resonance (NMR) – based metabolomics) to speed up drug
discovery form natural products especially when anti-viral constituents are investigated.
In this study very promising anti-HIV results were obtained from several aqueous
extracts (1:1 methanol/water) using a full virus model i.e. Helichrysum populifolium (IC50
12 μg/ml), H. appendiculatum (IC50 17 μg/ml), H. cymosum ssp. clavum (IC50 19 μg/ml),
H. oxyphyllum (IC50 19 μg/ml) and H. cymosum ssp. cymosum (IC50 21 μg/ml). With the
use of NMR-based metabolomics and multivariate data analysis (MVA) the specific
characteristic that differentiated the active extracts from the non-active extracts was
identified by making use of Orthogonal Projections to Latent Structures – Discriminant
Analysis (OPLS-DA). This characteristic was then used as a “blue print” or “fingerprint”
to guide the process of fractionation and purification. H. populifolium showed the highest
anti-HIV activity and thus was selected as the candidate extract for further analysis.
After a very quick and simple chromatographic fractionation process, seven fractions
were compared against the activity profile by making use of their NMR profiles, which
then visually indicated which of the fractions had the highest similarity. Fraction 6 had
the most similar “fingerprint”. The compounds of this active fraction were then identified
with the use of liquid chromatography – ion trap – time of flight (LC-IT-TOF) for quick
identification. The analysis revealed the presence of five chlorogenic type compounds,
3,4-dicaffeoyl quinic acid (DCQA), 3,5-DCQA, 4,5-DCQA, 1,3,5- tricaffeoyl quinic acid
(TCQA) and 5-malonyl-1,3,4-TCQA of which several are well known to have anti-HIV activity ranging from 0.85μM to 12μM. We were thus able to show with this study the
possibility of using NMR-based metabolomics guided fractionation to guide the process
of fractionation and identification from an active characteristic profile to the active
constituents within the active H. populifolium extract.
