What is fingerroot (krachai), and what is in the rhizome?

Fingerroot, called krachai (กระชาย) or krachai khao (กระชายขาว) in Thai, is Boesenbergia rotunda (L.) Mansf., a small plant in the ginger family. The part used is underground: a small central rhizome with a bunch of finger-like tubers growing from it. Its main compounds are flavonoids, chiefly pinostrobin, pinocembrin and panduratin A. Krachai dam (กระชายดำ) is a different plant in another genus, and the amounts of each compound in krachai khao vary with the plant part and the province.

In short:

• What it is: Boesenbergia rotunda (L.) Mansf., family Zingiberaceae; Thai names krachai, krachai khao
• Other names: fingerroot, Chinese keys, temu kunci (Malay)
• Main compounds: pinostrobin, pinocembrin, panduratin A, with others such as cardamonin
• Not the same as: krachai dam, which is Kaempferia parviflora (black ginger)
• What changes the amounts: rhizome or root, and growing province; in research, also the extraction method used for measurement
• Watch out for: people who are pregnant, breastfeeding or on regular medication should ask a doctor or pharmacist before using fingerroot products

What plant is krachai khao, and what else is it called?

Krachai khao is Boesenbergia rotunda, a plant in the ginger family (Zingiberaceae), the same family as ginger, galangal and turmeric. A 2012 review by Tan and colleagues says it grows in Southeast Asia, India, Sri Lanka and southern China. It was once placed in the genus Kaempferia but is now classified in Boesenbergia, and it has had eight different botanical names, including Boesenbergia pandurata, the name still seen in older papers.

Where does the name fingerroot come from?

The same review describes the underground part as a small, round central rhizome 1.5–2.0 cm across, from which several slender tubers grow in the same direction, like the fingers of a hand. That is where the English name fingerroot comes from.

What is known about its genes?

A 2022 genome study by Taheri and colleagues at the University of Malaya estimated the fingerroot genome at 2.4 billion base pairs, with 71,072 protein-coding genes, 72% repeated sequences and 18 pairs of chromosomes. The genome is highly heterozygous, meaning the two copies of each chromosome differ a lot.

What is the difference between krachai khao, krachai daeng and krachai dam?

The three names sound like colours of one plant, but only two of them are.

Krachai khao and krachai daeng

Tan and colleagues (2012) list Krachai and Krachai-Dang as Thai names for Boesenbergia rotunda, and explain that the colour of the central rhizome and the tubers depends on the variety: the yellow variety has bright yellow rhizomes, while other varieties have red or black ones. All are strongly aromatic, but they smell different from each other.

Krachai dam is a different plant

Krachai dam, known in English as black ginger, is Kaempferia parviflora. A 2022 study by Joothamongkhon and colleagues at Thailand's National Science and Technology Development Agency (NSTDA) collected it from 39 locations in Thailand. Using more than 3,000 genetic markers, the researchers found two groups that matched the colour of the leaf edge: a red-leaf type and a green-leaf type. Its main compounds are methoxyflavones, such as 5,7-dimethoxyflavone and 3,5,7,3',4'-pentamethoxyflavone, and the two types contain different proportions of them. These are a different group of compounds from the main ones in krachai khao.

What compounds are in the fingerroot rhizome?

The compounds most often measured in fingerroot are flavonoids, a large group of plant compounds. A 2025 study by Fahrudin and colleagues at Chiang Mai University found pinostrobin and pinocembrin to be the dominant phenolic compounds in fingerroot extract, and the 2025 Rangsit University study below measured pinocembrin, pinostrobin and panduratin A in the rhizome and root.

Source: formulas and molecular weights from PubChem. Pinostrobin and cardamonin share the same formula, C16H14O4: one is a closed-ring flavanone and the other an open-chain chalcone. Panduratin A is the largest of the four. Tan and colleagues (2012) also list other compounds found in the rhizome, such as alpinetin and boesenbergin A.

Which part has more, and does the province matter?

Both matter. A 2025 study by Monton and colleagues at Rangsit University analysed 32 fingerroot samples grown in different regions of Thailand using a validated HPLC method.

The limits: the abstract does not give the content of each sample or how many samples came from each province, so the provinces are shown as a group rather than ranked by number. The figures do not tell us how much fingerroot sold at markets contains.

Light and alkaline conditions

A 2025 study from the Faculty of Pharmacy, Mahidol University developed a method to measure pinocembrin, pinostrobin and panduratin A in fingerroot extract. In forced breakdown tests, all three were stable under acidic and oxidising conditions, but broke down readily under alkaline conditions and in sunlight. This was a laboratory test of an analysis method.

How have researchers extracted and measured fingerroot compounds?

To measure the flavonoids, researchers first extract them from the dried rhizome with a solvent. Fahrudin and colleagues (2025) bought fingerroot from the Chiang Mai University agricultural shop, freeze-dried and powdered the rhizome, extracted it in two ways, and measured pinostrobin and pinocembrin by HPLC.

Across the 30 test runs with carbon dioxide, pinostrobin ranged from 65.14 to 115.28 mg and pinocembrin from 8.27 to 62.10 mg per gram of extract. These are measurements of extracts made in a laboratory to study the method, using fingerroot from a single source.

How is fingerroot used in food?

Fingerroot is first a kitchen ingredient. Tan and colleagues (2012) say it is a common edible ingredient in Malaysia, Thailand, Indonesia, India and China, is usually grown in small home gardens, and is used to flavour curries and soups. In Thai cooking it goes into dishes such as nam ya (the fish curry sauce served with khanom chin), jungle curry and stir-fries.

A spice that is about 2,000 years old

A 2023 study by Wang and colleagues in Science Advances examined grinding stones from Oc Eo, a port of the early state of Funan in southern Vietnam that was in use during the early centuries CE. Among 316 starch grains from ginger-family plants, the researchers identified 31 that matched fingerroot, along with turmeric, ginger, sand ginger and galangal. They describe this as evidence of curry-making in Southeast Asia about 2,000 years ago, and note that fingerroot may have originated in Sumatra and Java.

Is there a recommended daily amount of fingerroot?

No. Fingerroot is a plant, not a nutrient, so it has no value in the Thai Reference Daily Intakes (Thai RDIs), which cover nutrients such as vitamins and minerals. As the tables above show, the amounts of its main compounds also differ widely between the rhizome and the root, and between provinces.

Who should be careful with fingerroot?

What safety studies exist

Tan and colleagues (2012) noted that, despite how widely fingerroot is eaten, its safety had not been scientifically established at the time, and that the studies available were in animals. In a 2024 Mahidol University study, rats were given one particular fingerroot extract formulation every day for 90 days, and no deaths or signs of toxicity were seen at the doses tested. This study does not tell us what amount is suitable for people.

People who are pregnant, breastfeeding or taking regular medication

Herbs can interact with some medicines. If you are pregnant, breastfeeding, take regular medication or are under a doctor's care, speak to a doctor or pharmacist before taking dietary supplements, and tell your healthcare providers about any herbs you use.

Dietary supplements are not intended to prevent, treat or cure any disease.