Has leukaemia met its Waterloo?

Although we may not appreciate this fact when we take our heavily packaged pills, tablets and capsules from the chemist, more than 50% of prescription drugs are derived from chemicals first identified in plants. Humans have been exploiting the plant resource in this way for millennia, and there’s every expectation that more drug discoveries will be made as new genetical-molecular technologies are employed and deployed.

Some indication of the untapped potential of this source comes from the fact that in areas such as Africa up to 80% of the population uses traditional medicine for primary health care, and it has even been disclosed that ‘Nearly one-third of Americans use herbs’ (although nearly 70% of those taking herbal medicines were apparently reluctant to tell their doctors that they used complementary and alternative medicine…).

Whilst some discoveries come from plants targeted solely for medicinal value, others come on top of existing nutritional benefits that long-established foodstuffs might have. Such seems to be the case of the avocado (Persea americana), which already has many well-established nutritional and health benefits.

Thanks to work by Eric Lee et al. we probably need to add anti-leukaemia properties to that multi-functional plant product as well. Leukaemia is the generic name for a group of human cancers that usually begin in the bone marrow and result in high numbers of abnormal white blood cells; globally in 2012, 352 000 new cases of, and 265 000 deaths from, leukaemia were recorded.

Whilst all human diseases are cause for concern, leukaemia is particularly distressing since it is the most common type of cancer in children, and its cause(s) is not always clear. Under the guidance of Professor Paul Spagnuolo of Canada’s University of Waterloo, the team have discovered that avocatin B – ‘a lipid derived from avocado fruit’, and known more formally as 16-Heptadecene-1,2,4-triol – 16-heptadecyne-1,2,4-triol (1:1) – has cytotoxic activity against acute myeloid leukaemia (AML). In particular, the avocatin targets the mitochondria of the AML stem cells and leaves healthy cells unaffected, and – importantly – this has been tested in human cells rather than non-human model systems.

In the understandably cautious world of rigorous, evidence-based testing of pharmaceuticals, it’s a long way from initial results – no matter how encouraging – to production of medicines that can be prescribed for this condition. However, the researchers hope to commence Phase I clinical trials in humans within the next year to take the work to the next stage in the lengthy process of drug development. So it’s just as well that ‘hungry humans saved the avocado’ (whose Aztec name apparently means testicle…) after the demise of the plant’s natural seed-dispersers during the Pleistocene extinction!

[And this work is on top of that by Li Wang et al. that shows that avocados ‘have beneficial effects on cardio-metabolic risk factors that extend beyond their heart-healthy fatty acid profile’ – Ed.]