Biochemical investigation of the upstream anti-sickling mechanisms of soursop (Annona muricata): 15-acetyl guanacone as an inhibitor of deoxyhaemoglobin polymerisation

Current sickle cell disease (SCD) therapies are limited and inefficient. The ethnomedicinal values ofAnnona muricatain the treatment of SCD, leading to this present research. Leaves and fruits ofAnnona muricatawere processed using solvent extraction and partitioning; aqueous, chloroform and ethyl acetate fractions.In vitro(anti-oxidant and anti-sickling), in silico, quantitative (amino acids) and kinetic simulation experiments were done. 15-acetyl guanacone, was used,in silicoagainst 2,3-bisphosphoglycerate (2, 3-BPG) mutase and deoxyhaemoglobin. The ethyl acetate and chloroform fractions better NO(BLACK CIRCLE)scavengers, iron-chelators and ferric reducing.In vitrounsickling (UT50) had ethyl acetate = 5 h and methanol = 7 h. Chloroform fraction hadEC(50)1.00 mg/mL (EC50= 546 mg/mL) to 10.00 mg/mL (EC50= 99 mg/mL).EC(50)andIC(50)of ethyl acetate fraction had steady-decrease. At higher concentration, chloroform fraction had higherBmax(1.48 x 10(21)U/mL) and higherKd(3.66 x 10(19) mg/mL), whereas, at a lower concentration, the ethyl acetate fraction demonstrated higherBmax(7.23 x 10(12)U/mL) and lowerKd(2.12 x 10(11) mg/mL); The relative affinity (BP) of chloroform fraction increased progressively with concentration. The amino acid profile revealed rich concentrations glycine, valine, leucine, lysine, phenylalanine, histidine, arginine, and tryptophan. From thein silicoexperiments, 15-acetyl guanacone specifically targeted the A and B chains, with greater affinity for the beta subunit. This suggested that 15-acetyl guanacone might be able to prevent the polymerisation of deoxyHbSS, induce an allosteric conformational change that increases the oxygen affinity, and decrease the cellular 2, 3-BPG concentration. Communicated by Ramaswamy H. Sarma