Identification of Phytochemicals, Adulterants and Contaminants in Selected Commercially-Available Anticancer and Antidiabetic Herbal Medicines in Kenya

Abstract

The number of people using herbal medicines to treat chronic conditions is increasing worldwide due to the perception that these medicines are safer than conventional pharmaceuticals. However, several studies have established that herbal medicines can contain synthetic and toxic natural compounds, undermining patient safety. Nonetheless, most countries, including Kenya, have a weak regulatory framework for herbal medicines despite their potential to harm consumers. In Kenya, most commercially-available herbal medicines have not undergone laboratory testing to determine if they contain synthetic contaminants, adulterants, or phytochemicals with relevant reported biological activities. This study addresses this gap by evaluating herbal medicines sold for diabetes and cancer treatment in Nairobi and Uasin Gishu Counties for phytochemicals, adulteration and contamination with synthetic compounds. 24 herbal medicines (9 anticancer and 15 antidiabetic) were collected from herbal clinics, herbal product manufacturers, herbalists, local retailers (supermarkets and nutrition stores), and hawkers/ street vendors in Uasin Gishu and Nairobi Counties. Gas chromatography- mass spectrometry (GC-MS) was used to determine the phytochemical profile of each herbal medicine. The GC-MS results revealed that all the sampled herbal medicines contained a wide range of phytochemicals with reported biological activities useful to diabetes and cancer treatment. They also highlighted the presence of toxic phytochemicals, including prunasin-d, 5-keto-d-fructose, and ketone, 7-methoxy-2-benzofuranyl methyl. GC-MS was also used to identify synthetic contaminants or adulterants present in the sampled herbal medicines. The results highlighted the presence of several synthetic compounds, including pharmaceutical salts, pesticide residue, and phthalates, which pointed to potential safety issues. Thus, this study developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous determination, identification and quantification of four commonly used antidiabetics – metformin, gliclazide, glimepiride, and glibenclamide - in herbal medicines. The developed method showed detection and quantification limits ranging from 2.86 to 7.67 ng/mL and 8.64 to 23.24 ng/mL, respectively. The precision of the developed method ranged from 8.5% to 18.1%, while accuracy was above 80% for all analytes except metformin (52%). This method was then applied to analyse the 24 sampled herbal medicines. Metformin was detected in 17% of the samples, at concentrations ranging from 900 ng/g to 1969 ng/g. Gliclazide, glimepiride, and glibenclamide were not detected in any sample. Overall, the study findings provide proof of adulteration of herbal medicines with pharmaceuticals. This adulteration undermines patient safety due to the potential for adverse herb-drug interactions. Therefore, market surveillance of herbal medicines sold in the country for toxicity, contamination and adulteration with synthetic compounds should be conducted and legislation that outlaws adulteration enacted.