There is a write-up on Cryptolepsis (p.25-26) in Stephen Buhner's 1999 paperback book Herbal Antibiotics, Natural Alternatives for Treating Drug-Resistant Bacteria
Copies are likely readily found via an amazon search (ISBN 1-58017-148-6).
Cryptolepsis is apparently active against Malaria, Staphylococcus aureus, Shigella dysenteriae, Neisseria gonorrhea, Escherichia coli, Candida albicans and Campylobacter .
Here is an excerpt from his book:
"Cryptolepsis has been found to be remarkably potent for malaria in human clinical trials.
One such trial compared the effectiveness of cryptolepsis with chloroquine, the usual synthetic drug for malaria treatment, in comparative patient populations at the outpatient clinic of the Centre for Scientific Research into Plant Medicine at Mampong-Akwapim in Ghana, West Africa.
Clinical symptoms were relieved in 36 hours with cryptolepsis and in 48 hours with choloroquine.
Forty percent of the patients using chloroquine reported unpleasant side effects necessitating other medications; those using cryptolepsis reported no side effects."
Boye, G. L. 'Antimalarial Action of Cryptolepsis sanguinolenta Extract:' The International Symposium on East-West Medicine, chapter 14, pages 242-255, 1989.
Cimanga, K., et al. "In Vitro Activities of Alkaloids from Cryptolepsis sanguinolenta." Planta Medica 62(1): 22-27,1996. Abstract.
"In Vitro and Vivo Antiplasmodial Activity of Cryptolepene and Related Alkaloids from Cryptolepsis sanguinolenta." J Natural Products 60(7): 688-691, 1997. Abstract.
Dean, Karen. "Cryptolepine Analogs" and "Cryptolepis." HerbalGram, no. 42, spring 1998, page 21.
Greller, P., et al. "Antitimalarial Activity of Cryptolepine and Isocryptolepine, Alkaloids Isolated from Cryptolepsis sanguinolenta." Phytother Res 10(4):317-321, 1996. Abstract.
Paulo, A., et al. "In Vitro Screening of Cryptolepsis sanguinolenta Alkaloids,." J Ethnopharmaco144(2):127-130, 1994. Abstract.