This search result for Sulforaphane cancer research shows what appears to be a fairly large amount of positive evidence for the usefullness of Sulforaphane in certain cancer prevention.
The primary natural root for getting sulforaphane is through eating Broccoli Sprouts or Broccoli. Is it worth seeking out these vegitables particularly for the sulforaphane or taking Broccoli Sprout extracts if you wish to avoid eating the fresh vegitables?
Any answer will reflect the values and judgment of the person giving it so it may be better in IMHO or GD at the mods discrestion. This is a non-issue for me because I love broccoli and brussels sprouts. Yummy-yum! I think I may have to go to the store now and get a big bag of broccoli florets so I can snack all day. Yummy-yum! YMMV considerably.
It’s found in all the cole crops, IIRC. That includes all the cabbages, cauliflower, and Brussels sprouts. So, don’t forget cole slaw, kimchi, and sauerkraut.
I found a good list of the ‘Cruciferous Vegetables’
Arugula
Bok choy
Broccoli
Brussels sprouts
Cabbage
Cauliflower
Chinese cabbage
Collard greens
Daikon
Kale
Kohlrabi
Mustard greens
Radishes
Rutabaga
Turnips
Watercress
But can’t yet find any statistics on the relative sulforaphane contents of each vegetable.
Does your list of 490 hits by google contain any actual data showing that sulforaphane is beneficial to actual living persons? And keep in mind there are tons of hits out there about the benefits of high dose vitamin supplements, but the actual meta-analysis of the studies out there showed that taking high dose of vitamin E (400 or more IU/day) caused an extra 39 deaths per 10,000 people vs. not taking vitamin E. (BTW, eating foods rich in vitamin E does seem to improve health and reduce mortality.)
What I’m saying is I’d look for real solid evidence that the substance is of benefit before leaping to take high doses in supplement form.
But I’d say eating a lot of the vegetables you list would be a good idea.
This list of sites looks intreguing http://www.ag.uiuc.edu/ffh/research1.html#Broccoli
and here is a link to Ohio State which has been the source of recent news stories about the possibilities of helping against Bladder Cancer.
I still don’t see any data suggesting that taking sulforaphane is safe or effective as regards either the treatment of or prevention of cancer. Just theoretical models, possibilities, and a few small studies, the best of which shows that guys who eat a lot of broccoli get bladder cancer less often than guys who don’t eat much broccoli.
I would say the data is lacking to recommend taking said supplement. I’ll fall back on my default recommendation: Stay healthy by eating sensibly (especially lots of fresh fruits and vegetables), exercising regularly, and avoiding vices like tobacco, drugs, or excess alcohol intake.
Thanks Quadgop it was hard making good sense of the bulk of that research, nore evaluating its overall value.
I know the feeling - I’m doing research related to the chocolate thread I started. It’s really hard to tease out the real meaning of medical research, especially since journal articles seem to be written with the assumption that the reader actually has an education in medicine.
Eat your broccoli. It’s good for you. Even if sulforaphane ends up not being a useful nutrient, you’re getting fiber, vitamin C, iron, calcium, vitamin A, potassium, folic acid, and very few calories.
But, mom, they taste like ick! 
Actually I quite like a little broccoli, I was more wondering if it is worth substituting in more cruciferous vegitables for regular vegies like peas, peppers, and spinach.