From the Catholic Encyclopedia
The family of liturgies originally used in the Patriarchate of Antioch begins with that of the Apostolic Constitutions; then follow that of St. James in Greek, the Syrian Liturgy of St. James, and the other Syrian Anaphorus. The line may be further continued to the Byzantine Rite (the older Liturgy of St. Basil and the later and shorter one of St. John Chrysostom), and through it to the Armenian use. But these no longer concern the Church of Antioch.
I. THE LITURGY OF THE APOSTOLIC CONSTITUTIONS
The oldest known form that can be described as a complete liturgy is that of the Apostolic Constitutions. It is also the first member of the line of Antiochene uses. The Apostolic Constitutions consist of eight books purporting to have been written by St. Clement of Rome (died c. 104). The first six books are an interpolated edition of the Didascalia (“Teaching of the Apostles and Disciples”, written in the first half of the third century and since edited in a Syriac version by de Lagarde, 1854); the seventh book is an equally modified version of the Didache (Teaching of the Twelve Apostles, probably written in the first century, and found by Philotheos Bryennios in 1883) with a collection of prayers. The eighth book contains a complete liturgy and the eighty-five “Apostolic Canons”. There is also part of a liturgy modified from the Didascalia in the second book. It has been suggested that the compiler of the Apostolic Constitutions may be the same person as the author of the six spurious letters of St. Ignatius (Pseudo-Ignatius). In any case he was a Syrian Christian, probably an Apollinarist, living in or near Antioch either at the end of the fourth or the beginning of the fifth century. And the liturgy that he describes in his eighth book is that used in his time by the Church of Antioch, with certain modifications of his own. That the writer was an Antiochene Syrian and that he describes the liturgical use of his own country is shown by various details, such as the precedence given to Antioch (VII, xlvi, VIII, x, etc.); his mention of Christmas (VIII, xxxiii), which was kept at Antioch since about 375, nowhere else in the East till about 430 (Duchesne, Origines du culte chrétien, 248); the fact that Holy Week and Lent together make up seven weeks (V, xiii) as at Antioch, whereas in Palestine and Egypt, as throughout the West, Holy Week was the sixth week of Lent; that the chief source of his “Apostolic Canons” is the Synod of Antioch in encœniis (341); and especially by the fact that his liturgy is obviously built up on the same lines as all the Syrian ones. There are, however, modifications of his own in the prayers, Creed, and Gloria, where the style and the idioms are obviously those of the interpolator of the Didascalia (see the examples in Brightman, “Liturgies”, I, xxxiii-xxxiv), and are often very like those of Pseudo-Ignatius also (ib., xxxv). The rubrics are added by the compiler, apparently from his own observations.