Antispermatogenic

A methanolic pod extract reduced fertility in male rats ^{1Reference 1Gupta et al. · 2004AnimalAntifertility effects of methanolic pod extract of Albizzia lebbeck (L.) Benth in male rats — animal modelView study →}, a bark extract — the medicinal part — produced antispermatogenic and antiandrogenic effects ^{2Reference 2Gupta et al. · 2006AnimalAntispermatogenic, antiandrogenic activities of Albizia lebbeck (L.) Benth bark extract in male albino rats — animal modelView study →}, and the bark saponins specifically were shown to act on the male reproductive system ^{3Reference 3Gupta et al. · 2005AnimalEffect of saponins of Albizia lebbeck (L.) Benth bark on the reproductive system of male albino rats — animal modelView study →}.

The finding therefore covers the preparation people actually use, not only the pod.

It is entirely rodent, from one research group, with no human fertility data and no dose-response in a preparation anyone takes.

The same result is examined as albizzia’s antiandrogenic action, and no study separates the two.

A dedicated study reported effects on spermatogenesis and the accessory reproductive organs in rats ^{8Reference 8Kholkute · 1977AnimalEffect of Hibiscus rosa-sinensis on spermatogenesis and accessory reproductive organs in rats — in vivoView study →}, sitting alongside the same programme’s anti-implantation work in the flowers ^{9,10,11Reference 9Kholkute et al. · 1977AnimalAntifertility potentiality of Hibiscus rosa-sinensis: parts of medicinal value, species and seasonal variation — ratView study →Reference 10Singh et al. · 1982AnimalAntifertility activity of a benzene extract of Hibiscus rosa-sinensis flowers in female rats — in vivoView study →Reference 11Pal et al. · 1985AnimalFlowers of Hibiscus rosa-sinensis, a potential contragestative agent: anti-implantation effect of the benzene extract — in vivoView study →}.

The male-side evidence is a single study within one research programme, with no independent replication and no human data.

The female half of hibiscus’s antifertility literature is considerably larger, and it is examined under antifertility.

Benzene and other leaf extracts produce a reversible antifertility effect in male rats, with reduced sperm count, motility and testicular androgen activity that normalises after withdrawal ^{12Reference 12Ahmed et al. · 2002AnimalReversible antifertility effect of benzene extract of Ocimum sanctum leaves on sperm parameters and fructose content in rats — animal in vivo studyView study →}. Anti-implantation activity is reported alongside it.

Holy basil is a daily adaptogen with roughly 24 human trials behind it and no serious adverse events up to eight weeks. It is taken for stress, mood and blood sugar.

Those trials measured cortisol, mood and glucose. None measured a semen parameter, so the human literature could not have detected this effect whether or not it occurs in people.

The evidence is animal and the effect is reversible, and the herb’s human safety record is good on every endpoint that has been measured.

Animal studies document both antispermatogenic and spermicidal effects for neem ^{13Reference 13Daniyal et al. · 2015ReviewAntifertility activity of medicinal plants — reviewView study →}.

Those are different mechanisms with different implications. Suppressed production is systemic and reversible in principle; a spermicidal effect is topical and immediate.

The review the finding reaches us through does not separate them, so neither the route nor the exposure that would produce either effect is defined.

Neem has decades of interest behind it as a botanical contraceptive, and none of that work has reached a human trial.