Onnit’s T-Plus supplement has added Long Jack root because of its ability to boost testosterone levels.  Long Jack root (Eurycoma longifolia, Tongkat Ali) has long been used for its medicinal properties for hundreds of years.  It has been used as an aphrodisiac and a way to boost testosterone levels.  Long Jack root has it origins in Indonesia, Malaysia and the far East.  The molecules that boost testosterone levels have been identified.  These testo booster molecules are known as quassinoids and ten variations on these molecules have been isolated and characterized in Long Jack.    

Testosterone is a steroid hormone that is responsible for developing male secondary sexual characteristics such as greater muscle mass, larger/denser bones, deeper voice, and facial/body hair.  Increasing testosterone levels is associated with building leaner muscle mass, increased strength, and decreases in fat content on the body. 

Although it is possible to take synthetic anabolic steroids to increase testosterone levels and build lean muscle, those steroids are not without adverse side effects.  Botanical sources of anabolic steroids like those found in Long Jack have been demonstrated to be effective and safe to take.  The lack of adverse side effects and easy availability make it a viable alternative for those of you who are bodybuilders.  And, Onnits’ T-Plus has made it convenient to take.      

Research demonstrates that men who have been administered 200mg of Long Jack extract daily for one month experienced a 47 percent increase in serum testosterone.  Men administered 100mg daily for 5 weeks also experienced similar results.  In fact, their muscle mass increased by over 2 kg and body fat was reduced by 3 percent.  Furthermore, another trial run was able to demonstrate that an increase in one-repetition maximum which means how much you can lift once, increased strength by 134 percent as compared to placebo controls.   

Long Jack has also been reported to increase sperm production and produce a delay in ejaculation and it is believed that the molecule 9-hydroxycanthin-6-one is responsible.  Long Jack is also reported to contain estrogen blockers, however these were in vitro studies and it is not known if these molecules are effective if taken orally.

Molecules found in Long Jack

  • Quassinoids:  150 different molecules have been identified but the two molecules with bioactive properties are eurycomanone and eurycomanol.
  • Eurycolactones:  longilactone and dehydrolongilactone
  • Cathin-6-one:  hydroxycanthin and methoxycanthin
  • Squalene derivatives:  eurylene, teurilene, and triterpenes
  • Tirucallanoids:  trihydroxytirucallendione
  • Eurypeptides:  proteins
  • Glycosaponins


Researchers took standardized bioactive fractions of Long Jack and tested them on male fertility and tried to determine the mechanism of action.  Powdered roots of Long Jack were extracted with methanol and water.  So they had four organic extracts (F1-F4) and a crude aqueous extract (W).  these were all standardized according to their respective major quassinoid content and profile.  The 4 F fractions were tested on rat spermiogenesis and were compared to the aqueous extract.  Sperm count was observed, sperm quality, and histological changes during the spermatogenesis cycle.  Fertility, plasma testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), and estrogen levels were measured after oral administration.  They also isolated testicular interstitial cells (Leydig cells) and observed the effects of quassinoids on testosterone release. 

Rats orally administered with F2 and W fractions increased sperm counts as compared to controls.  HPLC revealed that the F2 and W fractions were very similar in concentration of eurycomanone, the most bioactive component of quassinoids.  Light microscope examination of rat testicular tissue demostrated an increase in spermatocytes and spermatids in Stage VII of spermatogenesis as compared to controls.  The production of sperm and the number of Leydig cells had also increased.  The fertility index, fecundity index and pup liter size from females that mated with males treated with the F2 fraction had also increased.  Plasma testosterone levels were significantly higher on day 26 and 52 but dropped to control levels on day 104.  testicular testosterone, LH, and FSH levels were also significantly higher than controls, however plasma estrogen levels were significantly lower than controls.A standardized extract F2 of Long Jack quassinoids improved spermatogenesis by altering the hypothalamic-pituitary-gonadal axis (endcrine axis).

Testosterone and the Spermatogenic Process

The cellular pathways for the testosterone activation of the spermatogenic process has been mapped out.  The pathways have been divided into a classical and non-classical pathways in terms of testosterone activating the Sertoli cells of the testes.

In the classical pathway,  testosterone passes through the membrane (it’s lipid soluble) and binds to heat shock proteins (HSP )-AR transcriptional regulatory protein complex in the cytoplasm of the cell.  This causes the AR (androgen receptor) protein to change shape and break away from the testosterone-HSP-AR complex and travel into the nucleus of the Sertoli cell.  Once the AR protein is in the nucleus it binds to a specific DNA sequence known as the ARE (androgen receptor element) sequence and attracts either co-activators or co-repressors to regulate testosterone-mediated gene transcription.  If it attracts a co-activator, then the RNA polymerase will bind to the unit and begin making a copy of the downstream gene.  If a co-repressor binds, RNA polymerase will not be recruited and no gene will be read.  The presence of testosterone is not sufficient to activate gene transcription.  This is dependent on other molecules known as activators and repressors in the cell. 

The non-classical pathway is initiated by testosterone binding to the classical AR transcriptional regulatory protein usually at the internal aspect of the plasma membrane of the Sertoli cell.  The AR transcriptional regulatory protein interacts with an Src kinase enzyme and causes the Src enzyme to become phosphorylated (a phosphate atom is added to it to activate it).  The now activated Src then passes its newly gotten phosphate to an epidermal growth factor receptor (EGFR) to activate it.  Then EGFR passes its phosphate atom to a MAP kinase enzyme.  This activates the MAP molecular cascade by way of the Ras small G protein by phosphorylating it.  Then Ras phosphorylates Raf kinase enzyme and it phosphorylates the MEK kinase enzyme and that in turn activates the ERK kinase by phosphorylation.  Then ERK activates the p90RSK kinase enzyme in the nucleus by phosphorylating it and the p90RSK kinase activates the CREB protein in the nucleus by phosphorylation.  Now, the CREB can bind to a specific DNA sequence known as a cAMP response elements (CREs) where it will attract coactivators, RNA polymerase, and begin copying the downstream gene into mRNA.  Later, the mRNA will be translated into protein.  The non-classical pathway makes use of a series of phosphorylating enzymes (kinases) which is referred to as a molecular cascade.  Phosphates are high energy atoms that activate molecules to do work and they generally come from ATP the energy currency of the cell.


Onnit’s T-Plus is a powerful testo booster with its testosterone enhancer, Long Jack root.  Long Jack root has been scientifically demonstrated to boost testosterone levels.  The testo booster molecules contained within Long Jack have been identified as quassinoids and in particular eurycomanone and eurycomanol.  Increased levels of testosterone supports healthy spermiogenesis and libido as well as promoting greater muscle mass, strength, and lowering body fat content.  If you’re looking for a testo booster,  Onnit’s T-Plus may be for you.

Resource List:

Standardized quassinoid-rich Eurycoma longifolia extract improved spermatogenesis and fertility in male rats via the hypothalamic-pituitary-gonadal axis.


Combined Effects of Eurycoma longifolia and Testosterone on Androgen-Deficient Osteoporosis in a Male Rat Model


Molecular mechanisms of testosterone action in spermatogenesis




9-Hydroxycanthin-6-One Induces Penile Erection and Delays Ejaculation