There is a ton of info on L-dopa, mucuna pruriens and L-dopa vs mucuna pruriens on pubmed.gov. It’s pretty cheap if you know where to get it, especially if you get an extract. Remember extracts are much stronger.
L-dopa converts directly to dopamine, plain and simple. Besides increasing mood and libido directly, dopamine also has a direct effect on dropping prolactin. Prolactin, estrogen and to a lesser extent other hormones like testosterone provide feedback to reduce GnRH. That’s the hormone that leads to all the other sexual hormones and sexual function in general. Prolactin has a large effect on reducing it, but a small amount of prolactin is helpful for some sexual functions. The dopamine effect is immediate, within a couple minutes.
You don’t get high, addicted, withdrawal or dependence because unlike narcotics L-dopa does not force the release of dopamine. Your brain will take the extra and store it away. And then you have it for later, rather than a crash making you feel lousy and wanting more. Super high amounts of L-dopa for years, as used to treat Parkinson’s disease, leads to a drop of other neural hormones and related issues. It doesn’t reduce them directly like it does with prolactin. Rather since you are supplying too much of one and not others, the others eventually run low. Parkinson’s treatment attempts to supply some of these to some extent to mitigate the problem. Studies on mucuna pruriens, though limited, show that it has some effect on boosting other neural hormones leading to much less drawbacks. That’s why you should never get a 99% L-dopa mucuna pruriens extract. You are missing the other helpful compounds. Try something more like 10% of 20%. Also the amount used in Parkinson’s is 3-6 times the typical amount used for sexual reasons. Unless you go nutso on the dose for a decade you’ll be fine. But it probably would be a good idea to not use it for more than a year or two to be safe, and to keep the amount limited. I was using it for a couple years with no ill effects whatsoever, for the dopamine. Eventually I got that sorted out and didn’t need it anymore, so I figured that was a good time to stop. I have heard of some small issues with 99% L-dopa extracts. And if you use a lot at once of either it may feel a bit off, but it’ll pass in under 30-60 minutes.
At best it would be as good as HCG for PE and other hormonal purposes (GnRH leads to LH, and HCG is similar to LH). In reality because your brain stores away excess, it is much weaker than HCG. Many studies show a modest increase in sexual parameters like hormones and sperm quality. Besides the effect on sexual function, it increases libido a lot directly because of the dopamine. I doubt it would have any effect on PE, because AFAIK these things don’t affect PE.
SJW extract may help balance it out for some, but I don’t think it’s usually necessary. Unless you already have issues with low serotonin. Noni is nicer, but it takes a much higher amount.