New Drugs from Smelling Flowers

Eighty percent of the world’s population today has access only to traditional remedies prepared from local plants as solutions for healing. Pharmaceutical research and its associated industries exploit natural products and materials to search for and prepare active ingredients for use as medicines. It is estimated that more than forty percent of the new drugs registered in the last thirty years were obtained or derived from natural sources, or were inspired by natural compounds.

For centuries, humans depended exclusively on nature to find solutions for healing. The study of plant species has brought forth major contributions to medical knowledge and has lead to prototypes of major therapeutic drug classes; for example, cardiac glycosides from foxglove leaves (digitoxin), antimalarial drugs from cinchona bark (quinine), hypno-analgesic drugs from poppy latex (morphine), or anti-inflammatory drugs from white willow bark (salicylic acid). Additional studies have revealed evidence of their physiological receptors.

This widespread usefulness may be related to the fact that plants, being sessile organisms, chiefly depend on their own structure and composition to achieve biological, physiological, and ecological functions as well as to adapt and survive. Plants can't move, can't yell to chase away aggressors, and can't fend off predators or parasites. So, how have plants persisted for over 425 million years? The genome of the simplest plant, markedly larger than that of humans, encodes the expression of numerous, diverse and exclusive chemical entities that have complex functions and that interact with a variety of biological targets. Thus, plants and plant extracts are seen as large pools containing a huge diversity of compounds and, from the point of view of drug researchers and discoverers, they are valuable collections of exclusive chemicals that need to be investigated.

Some plants are adapted to produce and/or accumulate volatile compounds that easily diffuse in the surrounding atmosphere. Such compounds may be available to far-distant targets. Such plants, the so-called aromatic plants, can be recognized by their scents or fragrances, as a result of the interaction of their volatile compounds with the human´s olfactory receptors. Volatile compounds play important roles in the biology of aromatic plants, for example, attracting pollinators, inhibiting pathogens, and repelling predators. Natural selection has improved such compounds toward achieving the appropriate action on the biological target, and, not surprisingly, most such compounds fit the physical and chemical theoretical criteria needed to indicate the ability to diffuse through cell membranes or to cross biological barriers; in other words, to indicate their suitability to become a drug.

On this basis and profiting from the diversity of available aromatic plant species in Iberia, our group, at the Center of Pharmaceutical Studies, Faculty of Pharmacy, University of Coimbra, Portugal, using suitable methods of plant analysis and laboratory models of disease, undertook investigations to search for, within the huge pool of small, hydrophobic, volatile compounds typical from the aromatic plants, active compounds that have potential usefulness for maintaining human health.

Several of such plant extracts, fractions, and compounds are already known for their health-related activities; some for their ability to kill living targets, such as in the control of multi-resistant pathogenic yeasts, skin fungi, or infectious protozoa. Others are known as mediators of inflammatory responses or as inhibitors of key enzymes in some diseases. We hope, through our investigations, that some crude extracts that have low toxicity can be useful as low-cost alternative therapeutic agents to control fungal infections or protozoan parasites, particularly if made accessible to remote and/or disfavored populations. In addition, our investigations may reveal compounds that have enhanced efficiencies or improved mechanisms of action over existing drugs. Such results would open the way for the development of new innovative drugs.

It is worth mentioning that several important research achievements in this field of study have come from the investigation of endemic and/or endangered plant species. This reinforce the value of the biodiversity and the importance of a global conscience to preserving it throughout all the world habitats.