Enteric neurotransmission is inhibited by pure compounds isolated from Garcinia buchananii bark: (2R,3S,2?R,3?R)-GB-2, (2R,3S,2?S)-buchananiflavanone, and (2R,3S,2’’ R,3’’R)- manniflavanone
Thesis (M.S., Biology) -- University of Idaho, 2016 | Diarrheal diseases are characterized by increased intestinal secretion and hypermotility (peristalsis), which causes loose/watery stool and pain. Severe cases cause lowered immunity, dehydration, malnutrition and death. Children in developing countries experience 6-7 diarrheal episodes per year, and one in every five children under the age of five is killed by diarrhea. Current WHO recommendations for treating diarrhea are oral rehydration solution therapy (ORS, to combat dehydration), opiates (to combat the increased motility and pain) and if necessary, antibiotics. ORS cannot combat the duration or pain of diarrhea, and opiates are addictive, cause constipation and can cause paralytic ileus in children. There is a critical need for a novel therapy for treating diarrhea without such detrimental side effects, and natural products have the potential for such alternative drugs. In sub-Saharan Africa Garcinia buchananii bark extract (GBB) is a traditional medicine used to treat diarrhea and gastrointestinal pain. Previous experiments from our lab have demonstrated GBB’s anti-diarrheal, anti-propulsive motility, and anti-nociceptive effects. GBB is a non-opiod, neuroactive preparation that inhibits synaptic transmission. Some GBB derivatives retain the antimotility and anti-nociceptive effects, specifically the fractions PTLC1, PTLC5, M4, M5 and M7-4, isolated via Preparative Thin Layer Chromatography and High Pressure Liquid Chromatography. The primary components of these fractions are the pure compounds (2R,3S,2?R,3?R)-GB-2 (denoted as TDS1, of fractions PTLC1, M4), (2R,3S,2?S)-buchananiflavanone (denoted as TDS2, of fractions PTLC1, M5), and TDS3 (the structure of this compound is not yet known, of
fractions PTLC5, M7-4). MPLC fraction M3 does not retain anti-motility effects, but the primary component, (2R,3S,2’’ R,3’’R)-manniflavanone (denoted as TDS4), has been shown to inhibit L-type calcium channels. The central hypothesis of this project is that GBB and derivative compounds are an alternative, effective, novel, non-opiate, anti-diarrheal therapy or adjunctive therapy to ORS that mitigates diarrhea and pain by inhibiting the enteric nervous system’s (ENS) synaptic transmission and neuromuscular transmission. This study aims to elucidate which compounds within GBB cause inhibition of synaptic transmission and neuromuscular transmission, and subsequently, diarrhea. By using conventional intracellular microelectrode recording of porcine ileum smooth muscle inhibitory junction potentials (IJPs), and calcium imaging of post-synaptic calcium transients in guinea pig myenteric ganglia, we find that TDS1, TDS2 and TDS4 inhibit IJPs and post-synaptic calcium transients. Therefore, TDS1, TDS2 and TDS3 are likely the compounds within GBB that cause inhibition of neuromuscular transmission and synaptic transmission, and thus, inhibition of diarrhea.