Olive Leaf Extract, Standardized 18% Oleuropein, 100 Vegetarian Capsules, NOW FoodsOlive Leaf Extract is a natural botanical product that has been a subject of study since the early 1800's. This specific extract of olive leaves (Olea europea) is manufactured under strict quality control conditions. Why does Olive Leaf Extract in vegetable caps contain Silicon Dioxide? Silicon dioxide is a common excipient used in many encapsulated products, though some companies may not list it on their labels. It is a safe, hypoallergenic substance