Provided are liquid and powder grape extracts having elevated phenolic content. The extracts can be made from grape seeds, grape skins, or a combination thereof. In some instances, extracts may be blends of grape seed extracts and grape skin extracts. Methods of manufacturing such extracts area also provided. Such methods involve controlled temperature conditions to increase yield of phenolic compounds in the extracts. Methods of using the extraction for treating subjects are also provided, including treatment of cancer and end-organ damage relating to hypertension.

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