Have a look at the link below.

https://www.ebay.com.au/help/policies/prohibited-restricted-items/food-policy?id=4295&st=3&pos=3&que...

As you will be repackaging it there will be government food standards you will need to consider as you will no longer be a seller only but a manufacturer as well.  Check your state food authority for guidelines and requirements

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There are sure to be state regulations so as others have said, you'd be best to check those out before you buy a thing.

Once you are sure you comply with all those regulations, then you'd have to be sure you had professional packaging.

I buy several different food items from ebay from time to time and one thing I have noticed is the sellers are not supposed to claim health benefits for these items. Or put it this way, they have to be very careful how they word their ad.

You're saying to us that adding black pepper improves the health benefit but I am not sure if you'd be allowed to say that in the ad. It's something you'd need to check out.

Just as a guide, this disclaimer is from an ad for a spice.

Customer Information:

The information provided is intended as an information guide only and the user should determine if the product offered is suitable for their use. The user should obtain professional advice from a medical practitioner before use. We do not claim the product will result in a cure for any new or existing illness or ailment. We do not and cannot legally prescribe or advise on the use of this product. The user should be familiar with the use of herbs & powders and should seek professional advice if unsure.

Always store herbs and spices in a cool dry place out of sunlight.

a proper approved food handling kitchen.

Scientifically tested and proven document confirming your claims of health benefits,  not just jo blow stating it has health benefits.

Detailed packaging of exact contents, 

should I go on,  or you get my drift

Agree with all the advice / information supplied on this post so far, plus, in case I missed it,  you would need a good insurance policy if selling such a product. eg in the event that a buyer had a bad reaction.