Asam gelugur fruit
Garcinia atroviridis, known as Asam Gelugur, asam gelugo, or asam keping in Malay, is a large rainforest tree native to peninsular Malaysia. This species grows wild throughout peninsular Malaysia but is also widely cultivated, especially in the northern states, owing to its economic and medicinal value. Garcinia is a large perennial plant commonly found in evergreen forests in the southern region of Thailand and Malaysia. The ripe fruits are bright orange yellow, which are sliced, dried and used in curries or stewed in plenty of sugar to be eaten.
The fruit contains citric acids, such as tartaric, malic and ascorbic acids, hydroxycitric acid, and flavonoids. Sun-dried slices of the fruits, locally known as "asam keping", are commercially available and are popularly used as a vegetable salad and is considered extremely sour. Asam fruit contains various forms of fruiting acids-citric, malic, and tartaric and has been used for centuries by the Malaysian Kampung villages as both a cooking ingredient and weight loss agent.
A reasonable substitute is tamarind or key lime juice.