Toxicity

Passiflora nevertheless contain some very interesting and powerful substances which could become dangerous when concentrated. Learn more re toxicity here. Both foliage & unripe fruit are so bitter however that children are unlikely to be tempted by them. I have heard anecdotal evidence though of dogs becoming ill for a day or so after eating the (unripe?) fruit. Some people even prepare Passiflora to try to get a legal high. 

  Chemical makeup

Herbal Secrets of the Rainforest by Leslie Taylor lists Passiflora as containing Alkaloids, Alpha-alanine, Apigenin, D-fructose, D-glucose, Flavonoids, Gum, Gynocardin, Harmaline, Harmalol, Harmine, Harmol, Homoorientin, Isoorientin, Isovitexin, Kaempferol, Lutenin-2, Luteolin, Maltol, N-nonacosane, Orientin, Passiflorine, Phenylalanine, Proline, Quercetin, Raffinose, Rutin, Saccharose, Saponaretin, Saponarine, Scopoletin, Sitosterol, Stigmasterol, Sucrose, Tyrosine, Umbelliferone, Valine, Vitexin. 

Some of these compounds, like Gynocardin, are cyanogenic glycosides which when broken down will quickly release cyanide.

  Foliage

''Many Passiflora species are cyanogenic (Olafsdottir et al. 1989; Spencer 1988), that is they liberate hydrogen cyanide (HCN) when damaged...Most plants that are cyanogenic contain both a cyanogenic glycoside and the necessary enzyme (a b-glycosidase) that when combined during structural damage to the leaf, as they would be during herbivory, liberate HCN. In most cyanogenic plants, the cyanogenic glycosides are located within the vacuoles of cells while the enzymes are attached to the outside of the cell wall (Gruhnert et al. 1994). Therefore, for Cyanogenesis to occur cells must be lysed (broken) and the intracellular contents, include the vacular contents, must spill into the intercellular spaces. Because cyanide is toxic to so many species, cyanogenesis acts as a defense against many potential predators (Jones 1988; Nahrstedt 1985; Schappert & Shore 1999). However, to some species (including the two butterflies in the population study) that have adapted to use cyanogenic species as host plants, differing levels of cyanogenesis among individual plants may have implications for the use of plants in the population.

The Passifloraceae and allied families (including Flacourtiaceae and Turneraceae) possess an unusual HCN chemistry where the cyanogenic glycosides have a cyclopentenyl structure, that is, they are aromatic compounds with an additional 5-member ring (Tober & Conn 1985). Both a cyclopentenyl cyanogenic glycoside (gynocardin) and its specific B-glycosidase have been isolated from P. incarnata tissue (Spencer & Seigler 1984)...''

Extracts above from Cyanogenesis in Passiflora incarnata:
A PRELIMINARY REPORT
Rosbanak S. Masouri and Phil Schappert
Integrative Biology, C0930, University of Texas at Austin, 1 University Station, Austin, TX 78712-0253 Passiflora 12(2): 22-23