Which of the following is the main active ingredient of clove oil?

The correct option is Eugenol.

Step-by-step Explanation:

1. Understanding Clove Oil: Clove oil is an essential oil extracted from the clove plant, Syzygium aromaticum. It is widely used in traditional medicine, dentistry (as a local anesthetic and antiseptic), and as a flavoring agent.

2. Identifying the Main Active Constituent: The primary chemical component responsible for the characteristic aroma, flavor, and therapeutic properties of clove oil is eugenol. It typically makes up about 70% to 90% of the essential oil's composition.

3. Analyzing the Other Options:
- Curcuma: This refers to turmeric (which contains curcumin as its active ingredient), not clove oil.
- Malic acid: An organic acid found in fruits like apples, which gives them their sour taste.
- Tartaric acid: A crystalline organic acid found in many plants, notably grapes, bananas, and tamarinds.

Therefore, eugenol is the main active ingredient of clove oil.