Wu Huan Zi

Saponins isolated from Sapindus mukorossi were applied to human ejaculated spermatozoa and examined by scanning electron microscopy. The minimum effective concentration of 0.05 percent left surface topography unchanged after one minute but produced extensive vesiculation and disruption of the head-region plasma membrane after ten minutes; concentrations from 0.1 to 5.0 percent caused similar vesiculation, vacuolation and membrane erosion. The authors attribute the change to disruption of glycoproteins in the sperm plasma membrane lipid bilayer.

Saponin-enriched fractions from three plants were compared for haemolysis of 0.5 percent sheep erythrocytes and cytotoxicity to Vero cells. The Sapindus mukorossi fraction was by far the most haemolytic, with an HD50 of 18.0 plus or minus 1.9 micrograms per mL against 170.7 for Chlorophytum borivilianum and 736.7 for Silene vulgaris, and it was cytotoxic to Vero cells with an IC50 of 150.8 micrograms per mL. The authors conclude the Sapindus fraction is the least suitable of the three as a general saponin source on safety grounds.

A Sapindus mukorossi saponin fraction applied to a rabbit ear acne model for 14 days reduced lesion severity and pro-inflammatory cytokines in ear tissue and serum, lowered dihydrotestosterone and leukotriene content and shifted the skin bacterial community. Relevant to dosing: the fraction produced no acute or continuous skin or eye irritation in New Zealand rabbits only at concentrations below 50 mg/mL, which sets a practical ceiling for topical strength.

Sapindoside A and B together inhibited Micrococcus luteus more effectively than either alone. Microscopy showed loss of membrane integrity and leakage of cell contents; the ratio of saturated to unsaturated membrane fatty acids rose significantly and membrane fluidity, permeability and integrity all changed, with sapindoside A having the greater effect on permeability and integrity.

Ethanolic extract of Sapindus mukorossi fruit powder killed the vector snail Lymnaea acuminata with a 24 h LC50 of 2.75 mg/L, and the purified active component, identified chromatographically as saponin, gave a 96 h LC50 of 1.31 mg/L. The crude fruit powder was less potent (96 h LC50 119.57 mg/L). This quantifies how toxic the saponin fraction is to aquatic molluscs and is the basis of the drug's traditional use as a fish and snail poison.

Saponin from Sapindus mukorossi pericarp inhibited acetylcholinesterase, acid phosphatase and alkaline phosphatase in snail nervous tissue both in vivo and in vitro, competitively for acetylcholinesterase and acid phosphatase and competitively-non-competitively for alkaline phosphatase. The authors propose this enzyme inhibition as the mechanism of molluscicidal action, an activity distinct from simple surfactant lysis.

Saponins from Sapindus mukorossi added to nitrofurantoin or furazolidone produced more than 50 percent greater reduction in viable Gram-negative cells than antibiotic alone, with no toxicity to a human colon epithelial line. The saponins rendered the bacterial cell surface almost completely hydrophilic and shifted membrane fatty acids toward branched forms, showing high affinity for Pseudomonas cells.

Sapindus mukorossi extract combined with polymyxin B increased total bacterial membrane permeability beyond polymyxin B alone across Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Escherichia coli, with the clearest viability loss in Staphylococcus aureus, confirmed by confocal and transmission electron microscopy and by lipidomic and fatty acid methyl ester profiling.