Bitter gourd should be stored *with* its seeds intact for optimal freshness and to prevent it from drying out quickly.
When you remove the seeds from a bitter gourd, you expose the inner flesh to air, which accelerates the drying process and can lead to a loss of moisture and flavor. The seeds and the pithy core actually help to maintain the gourd's internal humidity and structure. To store bitter gourd properly, simply wrap the whole, un-seeded gourd in a paper towel to absorb excess moisture, then place it in a perforated plastic bag in the refrigerator's crisper drawer. This method helps to regulate humidity and prevent condensation, extending the gourd's shelf life. Only remove the seeds right before you intend to cook it.
If you find that your bitter gourd is starting to get too bitter, you can soak it in salted water for about 30 minutes before cooking. This helps to draw out some of the bitterness and make it more palatable.