Medicinal plants – Will Bidens pilosa prove to be a source of a new class of antimalarial therapies?

Mankind has used plants for medicinal purposes for centuries. The World Health Organisation estimates that 80% of Asian and African populations rely on traditional medicine for their primary health care needs. Of all medicinal plants found in the world, approximately 20% have undergone screening for therapeutic potential and validated. Bidens pilosa (B. pilosa) is one of the plants that has been screened and seems to be a promising target.

Bidens_pilosa_100227-0076_tdp

Photo Credit: Wikipedia

Background

B. pilosa is a weed which originates in Central America. It has the ability to thrive in almost any environment and is therefore, likely to occur in all countries. This plant reminds me of my primary school days. Walking back from school, exploring various shortcuts through the bushes and getting home hours later with a cardigan covered in Black Jack needles or as we call it in Zimbabwe “Tsine” (Shona). B. pilosa is known by various names in different countries; Picao preta (Brazil), Black Jack (South Africa), Beggars Tick (USA) and Xian Feng Cao (“Abundant Weed”) (China). B. pilosa is considered a major crop weed that is a threat to animals and a physical nuisance. However, is there more to this plant than meets the eye?

Medicinal uses

B. pilosa is used in traditional medicine, especially in Africa, for the treatment of wounds as an anti-inflammation and anti-bacterial for infections of the gastrointestinal tract. B. pilosa is also used in other parts of the world to treat various ailments. In Brazil it is used as a pain killer while the Chinese drink it in their tea as a treatment for diabetes and other conditions. The plants are ingested as teas and juice preparations which are also made into ointment for direct application onto wounds and burns.

What does science tell us?

Various compounds with therapeutic potential, mainly, polyacetylenes and flavonoids have been isolated and identified in all parts of the plant. Polyacetylenes have been shown to be highly toxic towards various pathogenic organisms and flavonoids reduce inflammation. These two categories of active compounds can help to explain the use this medicinal herb.

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An illustration of B.pilosa indicating medicinal uses of different parts of the plant (Belina Sithole)

In a study carried out by Rojas et al., 2006 B. pilosa extracts demonstrated antibacterial activity against E. coli and S. aureus. The antibacterial activity, ability to kill parasitic worms and protozoa shown by different extracts of B. pilosa are attributed to the presence of polyacetylenes (Bondareko et al., 1985; Geissberger and Sequin 1991).           B. pilosa is also used to treat stomach disorders such as peptic ulcers. The ability to diminish gastric secretion and cytoprotective effect – protecting cells from toxic chemicals of B. pilosa is attributed to the presence of flavonoids (Alvarez et al., 1999).

An endophytic fungus (Botryosphaeria rhodina) was isolated from the stems of B. pilosa. Extracts of the fungal isolate exhibited significant antifungal activity as well as potent cytotoxic – toxic to cells and antiproliferative effects – inhibit cell growth, against several cancer cells (Abdou et al., 2010).

B. pilosa root extracts contain polyacetylenes and flavonoids that exert in vitro antimalarial activity (Oliveria et al., 2004). Further research of B. pilosa has led to the isolation of two more compounds (linear polyacetylenic diol 1 and its glucoside 2), which demonstrated potent in vivo antimalarial activity (Tobinaga et al., 2009).

Conclusions

It is suggested that future antimalarial therapies containing B. pilosa extracts may become available to treat communities in Africa. The widespread use of this plant may yield valuable therapies to treat a variety of diseases, however, further studies especially cytotoxicity testing may be needed.

Definitions:

Cytoprotective: protecting cells from toxic chemicals or other stimuli

Antiproliferative: used to inhibit cell growth

Cytotoxic: toxic to cells

In vitro: observed in an artificial environment outside a living organism

In vivo: observed in a living organism

Flavonoids: common plant pigment containing flavone in various combinations, the compounds act as antioxidants

Flavone Capture

Polyacetylenes: an organic compound with a long chain of carbon atoms joined together with altering single and double bonds, each carbon atom bonded to one hydrogen atom

Polyacetylene Capture

References:

WHO Traditional medicine. 2008 World Health Organization; Available online: http://www.who.int/mediacentre/factsheets/2003/fs134/en/ (accessed on 11/02/2017)

Arthur, G.D., Naidoo, K.K. and Coopoosamy, R.M., 2012. Bidens pilosa L.: agricultural and pharmaceutical importance. Journal of Medicinal Plants Research6(17), pp.3282-3281.

Rojas, J.J., Ochoa, V.J., Ocampo, S.A. and Muñoz, J.F., 2006. Screening for antimicrobial activity of ten medicinal plants used in Colombian folkloric medicine: A possible alternative in the treatment of non-nosocomial infections. BMC complementary and alternative medicine6(1), p.2.

Bondarenko, A.S., Petrenko, G.T., Aizenman, B.E. and Evseenko, O.V., 1985. Antimicrobial properties of phenylheptatriyne, a polyacetylene antibiotic. Mikrobiologicheskii Zhurnal47, pp.81-83.

Geissberger, P. and Séquin, U.R.S., 1991. Constituents of Bidens pilosa L.: do the components found so far explain the use of this plant in traditional medicine?. Acta tropica48(4), pp.251-261.

Alvarez, A., Pomar, F., Sevilla, M.A. and Montero, M.J., 1999. Gastric antisecretory and antiulcer activities of an ethanolic extract of Bidens pilosa L. var. radiata Schult. Bip. Journal of ethnopharmacology67(3), pp.333-340.

Abdou, R., Scherlach, K., Dahse, H.M., Sattler, I. and Hertweck, C., 2010. Botryorhodines A–D, antifungal and cytotoxic depsidones from Botryosphaeria rhodina, an endophyte of the medicinal plant Bidens pilosa.Phytochemistry71(1), pp.110-116.

Oliveira, F.Q., Andrade-Neto, V., Krettli, A.U. and Brandão, M.G.L., 2004. New evidences of antimalarial activity of Bidens pilosa roots extract correlated with polyacetylene and flavonoids. Journal of Ethnopharmacology,93(1), pp.39-42.

Tobinaga, S., Sharma, M.K., Aalbersberg, W.G., Watanabe, K., Iguchi, K., Narui, K., Sasatsu, M. and Waki, S., 2009. Isolation and identification of a potent antimalarial and antibacterial polyacetylene from Bidens pilosa. Planta medica75(06), pp.624-628.

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