Mitochondrial Function as a Tool for Assessing Function, Quality and Adulteration in Medicinal Herbal Teas

Introduction

A review of current and historical herbal quality assessment methods revealed adulteration with low potency herbal material to be challenging. Mitochondrial functional analysis presents a novel opportunity to address this deficiency. Liquorice (Glycyrrhiza glabra L., Fabaceae) was selected as an initial herb to profile due to its ubiquity in herbal medicine and commercial teas.

Methods

MCF-7 and MCF-10A cells were seeded and treated for 24 hours with an original liquorice tea extract (OLTE; Three Licorice Tea; Pukka, UK) and subjected to mitochondrial functional assays. Use of pre-extracted material was selected as a method of functional adulteration and the effects of a pre-extracted liquorice tea extract (XLTE) was then compared to OLTE assays with significant results. HPTLC was used for comparison to existing industry methods.

Results

2000 μg / mL OLTE induced a 14.88% (p < 0.05) rise in reactive oxygen species (ROS) in MCF7 cells after 3 hours followed by a 14.73% (p < 0.05) drop at 72 hours. Oxygen consumption (OCR) rate dropped 72.6% (p < 0.01) and 85.16% (p < 0.01) in MCF10A cells treated with 500 and 2000 μg / mL OLTE respectively. The effects of mitochondrial modulating drugs were reduced in MCF7 cells pre-treated with 2000 μg / mL OLTE (oligomycin: 29.94%, p < 0.01; FCCP: 43.2%, p < 0.01; antimycin A & rotenone: 32.09%, p < 0.01). Further investigation revealed improved survival in 2000 μg / mL OLTE pre-treated MCF10A cells given cisplatin (50 μM: 11.79%, p < 0.05; 100 μM: 8.186%, p < 0.001), but had no effect on MCF7 cells. XLTE also demonstrated a 18.7% (p < 0.0001) drop in ROS in MCF7 cells treated with 2000 μg / mL at 72 hours but no effect at 3 hours. XLTE also decreased basal OCR in MCF10A cells at all doses (10 μg / mL: 21.12%, p < 0.05; 500 μg / mL: 53.52%, p < 0.0001; 2000 μg / mL: 56.41%, p < 0.0001), but no effect on drug resistance. HPTLC comparison revealed that differentiating OLTE from XLTE at identical strength was challenging.

Discussion

Possible mechanisms are discussed, proposing electron capture for the reduction in ROS and OCR without other modulations being observed, and efflux transporter expression explaining drug resistance. Drug resistance was the most consistent quality marker and is related to clinical use. Implications, further tests and generation of a mitochondrial functional testing pipeline are presented.