Here are my Cliff notes based on looking at the abstract. I don't know much biology so I'm not really clear on all the implications, but here's what I can understand:
First they studied the effect of kava on calcium channel receptors on white blood cells. They found that kava has some effect on several specific types of calcium channels. One of them, called TRPV1 is known as the "capsaicin receptor." We already know that kava effects calcium channels, but the new information here is that these are calcium channels on white blood cells. The author suggests this could have some implications for the functioning of the immune system, but they don't specify exactly what. They also suggest that some of the effect is caused by chemicals other than kavalactones, but don't break it down into the individual chemicals.
Second--and this the really strange part to me--they studied kava's microbiome. In other words, they grew some kava plants and studied the bacteria they found growing on the plants and in the dirt around the plants. They found that Hanakapi'ai and Papa 'ele 'ele have different critters in their microbiome, which is pretty remarkable. They also tested the effect of washing the dirt off the kava on the micribiome, which not surprisingly had an effect. According to the table of contents it looks like they also studied specific bacteria in kava's microbiome that could also be significant in the human gut microbiome, either as probiotics or pathogens.
(The second part of the thesis about the microbiome is not included in the preview, but I would actually be curious to see the details of that...)
EDIT: It's not clear what they found regarding human gut probiotics or pathogens in kava since that part the thesis isn't shown. Since it's not mentioned in the abstract, it could just mean they looked for probiotics and pathogens but didn't find any...
