Natural-Product-Based Solutions for Tropical Infectious Diseases

Abstract

About half of the world's population and 80% of the world's biodiversity can be found in the tropics. Many diseases are specific to the tropics, with at least 41 diseases caused by endemic bacteria, viruses, parasites, and fungi. Such diseases are of increasing concern, as the geographic range of tropical diseases is expanding due to climate change, urbanization, change in agricultural practices, deforestation, and loss of biodiversity. While traditional medicines have been used for centuries in the treatment of tropical diseases, the active natural compounds within these medicines remain largely unknown. In this review, we describe infectious diseases specific to the tropics, including their causative pathogens, modes of transmission, recent major outbreaks, and geographic locations. We further review current treatments for these tropical diseases, carefully consider the biodiscovery potential of the tropical biome, and discuss a range of technologies being used for drug development from natural resources. We provide a list of natural products with antimicrobial activity, detailing the source organisms and their effectiveness as treatment. We discuss how technological advancements, such as next-generation sequencing, are driving high-throughput natural product screening pipelines to identify compounds with therapeutic properties. This review demonstrates the impact natural products from the vast tropical biome have in the treatment of tropical infectious diseases and how high-throughput technical capacity will accelerate this discovery process.

Keywords: drug development; infectious disease; microbiology; natural products; tropics.

FIG 1

World map showing tropical regions. The geographical area between the Tropic of Cancer and the Tropic of Capricorn defines the tropics and occupies a large area of the Earth’s landmass and oceans. The tropics span 5 continents and are home to 43% of the world’s population, 80% of the biodiversity, 85% of the poorest people, and 41 infectious diseases. (Adapted from reference with permission of the publisher.)

FIG 2

Strategies for searching for novel drugs from natural products. Common strategies for discovering novel drugs from natural resources include random, chemorational, and biorational approaches. The biorational approach relies on ethnobotanically focused screening and ecologically directed screening. The chemorational approach is directed by chemotaxonomical considerations. The random approach relies on high-throughput screening with no prior ethnopharmacological uses or chemotypical rationality.

FIG 3

Visualizing drug delivery in the microvasculature. MacGreen mice were infected with Plasmodium berghei ANKA for subsequent intravital imaging of the brain microvasculature when the mice were showing clinical signs of malaria. Blood vessels were infused with tetramethylrhodamine-isothiocyanate (TRITC)-conjugated dextran (red). Moderate levels of leukocyte accumulation are seen both within and outside the blood vessels (green).