Well, I cooked up some cucuzzi edible gourd this weekend using a recipe for Sorakaya Sanagabedala Kura at Mahanandi. Despite reports from various sources (here, here, and here, for example) this gourd was not poisonous and tasted very good without a hint of bitterness. I tasted the gourd both before and after cooking and it was fine.
The bitter taste in the cucuzzi gourd (also known as bottle gourd, dudhi, and lauki) which makes it non-edible and potentially dangerous is from a chemical called cucurbitacin. There are many forms of cucurbitacins and they are common in all members of the squash family. Cultivated edible squash, melons, gourds, and cucumbers have low levels of these compounds but occasionally a plant may produce an over abundance of cucurbitacin making it poisonous if eaten. Soil infertility, drought, insect or disease pests, and genetics where the normally recessive gene that suppresses cucurbitacin expression is over-ridden are suspected causes for the excessive production of cucurbitacins that are normally scarce in edible fruits.
So back to cooking this harmless gourd. I cut down three huge gourds from the vines. After slicing them open I was happy to find that the insides were still very soft and tasted rather bland. Next, I cut the gourds into manageable pieces, peeled off the skins with a potato peeler, scooped out the seed cavity, and cut the gourd into half-inch sized chunks. I followed the recipe at Mahanandi, which is very spicy. I had to make a few modifications subbing garlic for asafoetida and dark brown sugar for jaggary. I used my own red pepper which is not a chili and even hotter. When everything was cooked there was about a pint and a half of gourd and peas in thin but very warm sauce. It was all very good and I will certainly be making more this week and will grow this fascinating plant again next year.