The goal of this clinical trial is to compare the effect of apigenin supplementation in freezing medium with no apigenin supplementation in freezing medium on post-thaw human sperm motility. It will also evaluate the sperm viability, total antioxidant capacity, and oxidative stress markers. The main questions it aims to answer are:

• Does apigenin supplementation in freezing medium improve the post-thaw sperm motility?
• Does apigenin supplementation in freezing medium improve the post-thaw sperm viability, total antioxidant capacity, and oxidative stress?

All normal semen samples from participants who give written informed consent and meet the eligibility requirements will be included in the study. Prepared semen samples were divided into 3 groups.

1. Pre-freezing sperm suspension
2. Frozen-thawed control without apigenin supplementation in freezing medium
3. Frozen-thawed sperm suspension with apigenin 0.2 mM supplementation in freezing medium Baseline sperm motility will be measured in pre-freezing sperm suspension. The last 2 groups will be stored in liquid nitrogen for at least one week. After thawing, the sperm suspensions will be evaluated for motility, viability, total antioxidant capacity, and oxidative stress markers.

Inclusion Criteria:

• Healthy men aged 18-45 years who can receive semen analysis services at the Reproductive Biology Unit, Chulalongkorn Hospital, Thai Red Cross Society
• Normal semen analysis results according to the World Health Organization criteria (Volume ≥ 1.4 mL, Sperm concentration ≥ 16 million/mL, Total motility ≥ 42%, Progressive motility ≥ 30%)
• Giving consent

Exclusion Criteria:

• A history of accidents, radiation to the testes, or a history of male reproductive system surgery
• Undescended testis
• Varicocele
• A history of taking certain medications that affect sperm production, such as chemotherapy, hormones
• Currently having sexually transmitted disease

You can ask for information directly from the investigators.