28-Homobrassinolide is a brassinosteroid found in minute quantities in the pollen of Chinese cabbage, and it helps boost rats' strength and muscles, write researchers at Rutgers University in FASEB Journal.
Plant steroids are nothing new. Supplements containing ecdysteroids or sterols have been on the market for years, and recent studies have shown that even apple peel contains an anabolic plant steroid compound. That plant-based brassinosteroids have an anabolic effect is news. Brassinosteroids are plant hormones that stimulate growth. The faster a plant grows, the more active brassinosteroids it has in its cells. That's why vegetable sprouts contain brassinosteroids, but even in these the doses are so low that they have hardly any effect on muscle growth.
Farmers in Asia use synthetic brassinosteroids as a growth promoter on their crops. Western farmers don't – their plants get so much artificial fertilizer and pesticides that brassinosteroids hardly cause a reaction.
The researchers had already published the results of a cell study which indicated that brassinosteroids had an anabolic effect, but in their most recent article they describe the effects of synthetic 28-homobrassinolide [structural formula shown below] on rats. The compound boosts the activity of the anabolic signal molecule Akt in muscle cells.
The figure below shows the effect of a 10-day orally administered course of 60 mg 20-homobrassinolide per kg per day on the strength in the fore and hind limbs of untrained rats. The second figure compares the effect on the calf muscle of oral administration and – in lower doses – injections.
The brassinosteroid is most active in the fast and powerful type II muscle tissues.
The tables below show the effects of 10 days of oral administration of 28-homobrassinolide on the body composition of male rats that don't make testosterone [ORX]. The researchers gave one group of rats feed consisting of 24 percent protein [Normal diet]; another group got feed consisting of 40 percent protein [High-protein diet]. The hope was that the anabolic effects of a protein-rich diet and 28-homobrassinolide would mutually reinforce each other, but that didn't happen.
The rats did no exercise. Perhaps if they had trained the results would have been different.
The table below compares the effects of good old testosterone with those of 28-homobrassinolide. The greater the effect on the prostate, the greater the chance of androgenic side effects; the greater the effect on the levator ani, the greater the muscle strengthening effect. It is clear that 28-homobrassinolide has no effect on the androgen receptor. And what is also clear is that the anabolic effect of testosterone is greater than that of the brassinosteroid.
"28-Homobrassinolide was safe in rats when tested at doses up to 1000 mg/kg", the researchers write. "At the same time, brassinosteroids caused cell cycle arrest and apoptosis of human breast cancer cells when tested at doses > 30 microM, without affecting the normal nontumor cell growth of BJ fibroblasts". And that's good to see: an anabolic substance that doesn't increase the risk of cancer – but actually reduces it.
FASEB J. 2011 Oct;25(10):3708-19.