Well, I don't know if the information on 2-Hydroxy-1,4-naphthoquinone is correct, but henna is a brown-red plant material that my girlfriend usess to dye her hairs with. It is therefore not a pure compound, but if the concentration is high enough I guess you could extract the quinone, but it might bee difficult to purify.
Henna aka Lawsonia inermis (http://reverndbunny.sphosting.com/growhenna.html)
(http://reverndbunny.sphosting.com/growhenna.html)
Composition:
http://www.ars-grin.gov%3A8080/npgspub/xsql/duke/plantdisp.xsql?taxon=547 (http://www.ars-grin.gov%3A8080/npgspub/xsql/duke/plantdisp.xsql?taxon=547)
(change %3A in the above link into : to make it work)