Zanthoxylum dipetalum is a rare species of tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

 in the citrus family

Rutaceae

Rutaceae, commonly known as the rue or citrus family, is a family of flowering plants, usually placed in the order Sapindales.Species of the family generally have flowers that divide into four or five parts, usually with strong scents...

 known by the common name kawa'u. It is endemic to Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, where it grows in forests on 3 or 4 of the islands.

There are two varieties.

• Z. d. var. dipetalum is present on Kauai
  Kauai
  Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...
  
  , in the mountains of Oahu
  Oahu
  Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...
  
  , on Hawaii
  Hawaii (island)
  The Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the North Pacific Ocean...
  
   in Hawaii Volcanoes National Park
  Hawaii Volcanoes National Park
  Hawaii Volcanoes National Park, established in 1916, is a United States National Park located in the U.S. State of Hawaii on the island of Hawaii. It encompasses two active volcanoes: Kīlauea, one of the world's most active volcanoes, and Mauna Loa, the world's most massive volcano...
  
  , and possibly on Molokai
  Molokai
  Molokai or Molokai is an island in the Hawaiian archipelago. It is 38 by 10 miles in size with a land area of , making it the fifth largest of the main Hawaiian Islands and the 27th largest island in the United States. It lies east of Oahu across the 25-mile wide Kaiwi Channel and north of...
  
  .
• Z. d. var. tomentosum is known from fewer than 30 individuals on Hualālai
  Hualalai
  Hualālai is a dormant shield volcano on the island of Hawaii in the Hawaiian Islands. It is the third-youngest and the third most active of the five volcanoes that form the island of Hawaii, following Kīlauea and the much larger Mauna Loa, and also the westernmost. Its peak is above sea...
  
   volcano on Hawaii. This variety is a federally listed endangered species
  Endangered species
  An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
  
   of the United States.

The roots of Z. dipetalum have been found to contain several chemical compounds, including canthin-6-one, chelerythrine

Chelerythrine

Chelerythrine is a benzophenanthridine alkaloid extracted from the plant Greater celandine . It is a potent, selective, and cell-permeable protein kinase C inhibitor....

, nitidine, tembetarine, avicennol, xanthoxyletin, lupeol

Lupeol

Lupeol is a pharmacologically active triterpenoid found in a variety of plants, including mango and acacia visco. It has several medicinal properties, one being anti-inflammatory...

, hesperidin

Hesperidin

Hesperidin is a flavanone glycoside found abundantly in citrus fruits. Its aglycone form is called hesperetin. Its name is derived from the Hesperides nymphs of Greek mythology. Hesperidin is believed to play a role in plant defense. It acts as an antioxidant according to in vitro studies...

, sitosterol, and magnoflorine.